Top-end digital concerns [Archive] - Large Format Photography Forum

Clement Apffel

12-Jan-2009, 04:21

After a lot of time spent reading technical reviews and articles, I still do not understand some of the major concern of current digital hardware.

My main interrogations are about the physical size of pixels:

In the first hand we have very respectable theoretical calculation about the diffraction related with the diameter of the pixel size. Those calculations bring us to many known facts like those:

Under the size of 9 nanometers, the image quality falls quite hardly. The ratio signal / noise forces to use heavy corrections in the DSP.

With a given pixel size, you won’t be allowed to close your aperture more than a given value under which the size of the Airy disc becomes greater than 2 pixels diameter and makes the capture quality fall drastically.
This value is known as being 2.12*pixel size (in nanometers)
Example: the Canon EOS 5D has 8 nm pixels. 2.12*8=16.96. that means that you can’t close your diaph under f/17. and that is not related to focal length nor CCD size. It is just a plain relation between pixel size and Airy disc diameter.

And on the other hand we have gear producers that continue the Mpixels race.
In February 2k8 Sony announced its 24.6 Mpixel 24x36 mm CMOS and few month later Nikon uses that CMOS in its D3x.
That is 6.4nm pixels.

Digital backs show pixel size between 5 and 7 nm too. And one wouldn’t be a fool to bet on the fact that future releases will show more pixels on same sized sensors.

So what is all that about? I’m getting confused.
And one can find almost none field feedback about those aperture / pixel size problem. It doesn’t appear to be a well known technical issue.

Is it just theoretical hair splitting ?
Is it just commercial big numbers war unrelated with the image quality?
Do I miss something big somewhere?

I guess that the DSP corrections are getting better and better. But does that mean gear producers renounced to perform optimal capture and few corrections in their devices?

I can understand that a 300$ point and shoot camera is designed with 3nm pixel size, cheap sensor, plastic lens and MASSIVE DSP corrections.
But what about top-end professional digital gear?

With film, I have a 100% control on gear, film, processing and almost a 100% understanding of each.

To me it is very frustrating to use or be forced to use a gear that I do not fully understand. (digital MF/LF devices)
Not knowing and not controling what happens in the magic box (DSP), not knowing the technical trade-offs that are made by gear producers on sensors is unacceptable to me.

So that is why I would like to start a discussion of this kind on my favourite photography forum.

I am aware that this topic is not 100% related with LF. But I didn’t feel like starting this thread in the lounge!
Moreover it is about current concern on photography. And my worry in this topic is top-end quality just as in my LF work and LF topics.
And finally I am curious to read the opinions of the experienced photographers and the optics experts roaming on that forum.

Regards,
CA.

PS : I hope my english isn’t too much of a pain to read.

Aender Brepsom

12-Jan-2009, 04:56

Emmanuel BIGLER

12-Jan-2009, 07:19

Hi Clément

Following your post, the question relevant to large format users are
- since digital is supposed to deliver better images than film with he current "35mm" (24x36mm) and medium format silicon sensors (now close to the 41x56 = 645 film size), with a better work-flow and (hopefully) with a better cash-flow (for professionals), is there any future for even 6x8 cm silicon chips and above ?
- if large format silicon chips appear, the question of 3 micron pixel size is less important provided that we have enough pixels to saturate even a one terabyte hard disk with 2-3 images ;)

Regarding smaller pixel size, we should always make a difference between
- pixel pitch or pixel grid periodicity, commanding the rules for the sampling theorem
- pixel surface, commanding the number of photons per exposure for a given illumination and exposure time, hence commanding the physical signal to noise ratio.

Sure, in Bayer patterns both pitch and aperture size are related for practical reasons, but both phenomena are formally different. Reminder : the commercial pixel count for a Bayer pattern is the total number of pixels all colors combined, in fact the actual pitch for red pixels is twice as big as the basic Bayer pattern pitch.

I see a great deal of interest in tiny subpixels as exposed below.

Regarding the sampling theorem I prefer not to speak in terms or Airy disks but in terms of cut-off period or cut-off spatial frequency.
With film we are in a situation of the cut-off period of best films is far above what can pass through a top-class large format lens. So in a sense, all LF users are very happy with a detector which is much better than the lens ! So why not the same for digital photographic imaging, not only for military or aerospace use (or both ;) ) ?

The absolute cut-off period for a diffraction-limited lens si N*lambda where N is the f-number and lambda is the average wavelength of visible light ; in fact taking the worst-case at 0.7 microns (the actual limit of sensitivity fr the human eye) we get an ultimate cut-off period of 0.7 N.
The sampling theorem states that you need 2 samples per optical period to avoid aliasing and moiré effects.

Take a state of the art view camera lens, e.g. a solid modern 150mm for 4x5", consider that it is diffraction-limited at f/16, the diffraction cut-off period is about 11 microns (0.7 * 16), the corresponding cut-off spatial frequency being about 90 cy/mm, a figure hardly reached by any view camera lens covering the 4x5" format. Modern color film are capable of recording fine details above 100 cy/mm but with a vanishing contrast.

I recenty read that Sony has announced silicon chips for mobile phones with 12 Mpix on a sensor with 7mm of diagonal, 3288 x 2468 pixels ; this yields a pixel pitch of 1.7 micron (we know nothing from these figures about pixel surface, smaller than 1.7 x 1.7 micron square !)
http://mobilearsenal.com/new/sony_12_mp_and_wide_angles_for_mobiles.html

So a pixel pitch of 1.7 microns yields a cut-off period of 3.4 microns, this corresponds to a diffraction-limited lens at about f/5. For a fixed-focal length for a mobile phone, if it is not a wide-angle, why not ? But sure, we are now entering a situation where the optical diffraction cut-off frequency of the lens is the actual limit.
To me this is a blessing since in this perspective we can forget about anti-aliasing filters. Good by also to anti-moiré post-processing software as advertised by Hasselblad !

Compare with the situation we have in LF on film.
If you read the actual MTF data of a fine-grained color slide like PROVIA 100F, you find that the MTF curve of this film is very close (up to 60 cy/mm) to the MTF curve of a 7-micron pitched sensor fitted with an anti-aliasing filter cutting off at 70 cy/mm, except that film transmits fine details with a low contrast well above 100 cy/mm.
Since you are French you can read my article here and check by yourself.
http://www.galerie-photo.com/film-contre-silicium-resolution.html

But we can use (B&W) films for which the MTF extends above 200 cy/mm, the Gigabit(TM) film was available in 4x5" ! So why not doing the same with digital sensors ?

Regarding tiny pixels, I see a great interest in them since it gives a total freedom to the digital imaging software engineer to do as much pre-processing as thay can inside the camera, or inside the digital back before delivering the actual image file to the end user.
Once the software is developed, it is costless to duplicate it. And the computations are secret and proprietary, do not expect any details about that.
In Europe we do not recognize software patents, so all pre-processing tricks, at least for the European market, will be secret know-how. And if a company is issued a software patent for digital image pre-processing valid only on the US, taking into account that you have to disclose a minimum of technical details in a patent, this would mean that the patent is kept secret for European readers ! ;)

So on the contrary I'm expecting that zillions of tiny pixels will continue to be both a marketing gimmick for the years to come, and a blessing for software engineers. It will give them so much freedom in pre-processing, that the question of the optical diffcation cut-off frequency wil be more or less marginal.
I'm thinking of all kind of intelligent pre-procesing software based on smartly combining pixels together, in a adaptative way, testing locally the shapes and intensities in the image, in order to reduce noice where it is the most visible and to enhance egde sharpness ad libitum.
Instead of good old Fourier methods based on a spatially invariant linear processing, I see a heavy use of all kinds of non-linear and adaptative image pre-processing techniques based on brute-force methods with zillions of pixels !

neil poulsen

12-Jan-2009, 14:35

You're taking an interesting approach to this problem. As attracted as I am to technical detail, I'm taking a more emperical approach to this question. But, this may be all the more appropriate, since my interest is more in the low end.

I've been doing a lot of reading, and here are a couple of conclusions that I've drawn:

As for 35mm DSLR full-frame cameras, the current high-end DSLR's in the low 20's megapixels offer about as much resolution as current, high-end DSLR zoom lenses can handle. Maybe one can go a little higher with fixed focal length lenses.

I spoke with Schneider LF technical people, and it was their opinion that at 22 megapixels, one could use traditional LF lenses and not expect to gain that much by "upgrading" to the Digitar type lenses. (I'm thinking in particular of the Mamiya 22mp digital back.) They emphasized that a lot could be accomplished, size-wise and otherwise with a back like that. Above 22p, they recomended more sophisticated lenses.

So, given the expenses involved, this is the direction towards which I'm heading. 22mp can do quite a lot. It'll take a while, but at least I have a plan. While I found an older style Arca 6x9 camera for a reasonable price, I've recently run across a way I can adapt this back to my 4x5. Etc.

About three and a half years ago, I purchased the only full-frame camera that I could afford. There were only two: the Canon 1Ds and the just discontinued Kodak DSLR in either a Nikon or a Canon mount. I wanted to use a 24mm PC lens, so I needed full frame, to get the best wide-angle advantage of that lens. Given the hefty discount, I chose Kodak in a Canon mount. It has it's weaknesses and strengths. It's low ISO, but I use it only on a tripod like a VC. One thing I like, it has no anti-aliasing filter. This gives it excellent color and resolution characteristics. (Until moire interferes.) One advantage to this camera, is that it's good preparation for using a digital back, since they also do not have anti-aliasing filters.

But, there are negatives with the 35mm DSLR approach. Movements are more limited, given the few number of lenses that can be PC controlled. The exposure chamber is small, so DSLR's are more subject to flare,especially in overcast situations. (I hate flare!)

Digital is expensive. A I kind of implied, the direction I'm taking is more driven by what I can achieve, what's available, and a principle of diminishiing returns as one scales the digital ladder.

Gordon Moat

12-Jan-2009, 15:54

A short time ago I commented upon this exact aspect of sensors, yet there were no responses:

http://www.largeformatphotography.info/forum/showpost.php?p=417531&postcount=21

The main issue really is the pixel cell site dimension. While I think a near 4x5 sensor could be possible, there would not be any advantage in having it near 6µm pixel sizes. Without doing the math on this, I would propose that 9µm might be a reasonable limit, and allow some usable apertures and image quality.

One could cram even more pixels into a sensor than can be found on a Nikon D3X, but to do so would sometimes be even more of a compromise of image quality. It would also mean that smaller apertures would degrade image quality even more.

Another possible approach would be doubling of cell sites; imagine a future D6X with close to 52MP sensor. The only practical way to do that would be to double up (or more) the captures, then interpolate into a smaller result. A few small video cameras do that; they have sensors near 5MP and group together four or more adjacent pixels to create a more sensitive signal to produce a lower resolution HD result.

However, I think that the current D3X really is at the performance limit; to go further would have extremely low improvement in optical resolution (not file sizes). I really feel that with the Canon 1Ds Mark III and Nikon D3X, those companies need to concentrate more on improving colour and sensitivity, and give the uberMP race a rest for a while.

Ciao!

Gordon Moat Photography (http://www.gordonmoat.com)

Noeyedear

12-Jan-2009, 17:06

Hi Clement,

my answer will not satisfy you at all, because I am quite the opposite of you regarding technical details. I don't invest my time in understanding all the technical aspects of a DSLR camera, but just use it as a tool for my purposes. There are limitations, but compared to 35mm film, a camera like the 5D or the 1Ds Mark II/III has nothing but advantages. With 35mm lenses, you couldn't stop further down than f/16 either without getting diffraction issues. This is not different with FF DSLR bodys.
Again, I do not care much about technical details, but I just see the excellent results from my 1Ds III and that is enough. For me, with prints up to 1m large, the only (but very important) advantage of LF over DSLRs are the movements. If I could have the movements on a DSLR (more than with a few tilt-shift lenses), I probably wouldn't use a LF camera any more.

Strange how people see things differently. I also have a 1DsmkIII, I'm sort of disappointed with it, not that it does not perform very well, it does mostly. It leaves me thinking it should be better, hence a return to LF for me for the fun side of photography. The more pixels I have in 35mm cameras the more I like film. I've not found any Canon lenses to get me excited either. The latest range of pixel packed 35mm just leave me cold, all those pixels help highlight digital faults and make me realise how good film is and how I took it for granted.

Kevin.

Eric Leppanen

12-Jan-2009, 19:28

...I think that the current D3X really is at the performance limit; to go further would have extremely low improvement in optical resolution (not file sizes). I really feel that with the Canon 1Ds Mark III and Nikon D3X, those companies need to concentrate more on improving colour and sensitivity, and give the uberMP race a rest for a while.Thom Hogen seems to reach the same conclusion in his review of the D3x (http://www.bythom.com/nikond3xreview.htm). Some excerpts:

...I would say that f/11 is that last aperture you can use and still have an expectancy of getting near maximal resolution (a term I loosely used before: diffraction limited aperture). Go smaller than f/11 and no amount of careful sharpening will restore the semblance of acuity at and near the Nyquist limit. Moreover, you'll lose signficant contrast, and most people perceive contrast in conjunction with sharpness (i.e. more contrast is perceived as "sharper"). If you're a stickler for detail, don't stray past f/8...For my landscape work, I won't be afraid to use f/11, but if I can get to f/8 I will.

...Indeed, I think that the serious landscape shooter almost certainly needs to consider using the PC-E lenses on his D3x and using the Scheimpflug principle to get depth of field, not solely aperture. If you need to go to f/16 for depth of field in your landscape work, I'm not so sure that you shouldn't just use a D700 and use panorama stitching to get more pixels, despite what that means for moving subjects.

Since I know from 35mm film experience that I can't get traditional near-to-far landscape compositions in full focus at f/8 (and frequently not even at f/11), it would seem that to achieve optimal landscape resolution with a 20+MP DSLR kit, I'd be limited to three tilt/shift lens focal lengths (with limited coverage compared to their LF film counterparts); above and beyond that, I'd have to shoot planar or limited depth-of-field subjects. A lot of folks are perfectly happy shooting 4x5 film with just three lenses (90, 150, and 240 are roughly comparable to the DSLR tilt/shift focal lengths), but I'm not. And stitching is of limited appeal since most of my subjects involve moving objects.

So it would seem that 35mm DSLR's can intrinsically achieve some LF film landscape photography objectives, but not all; and that further ratcheting up the megapixels will achieve little to no benefit due to diffraction. Apparently the only way in the foreseeable future to achieve all LF film camera capabilities with digital capture is to use a technical camera with a digital back. A used 22MP digital back can be cost-effective if one is happy with a maximum 16x20" print size (it would yield roughly 260DPI, which is close to the optimal 300+ DPI used by most inkjet printers), or can shoot subjects amenable to stitching. But the higher capture resolutions required for larger native print sizes are just not cost-effective at this point.

The potential of digital capture is certainly intriguing (the faster shutter speeds by itself would enable a variety of shots not possible with LF film), but for now I'm waiting until the MF digital market shakes out and prices come down quite a bit. And with a deep recession underway, that could take a long time.

Lenny Eiger

13-Jan-2009, 11:43

Clement,

I think there are a lot of numbers out there. Some of them mean something and some of them don't. For commercial work, the convenience of digital and the small target size (magazine page) make it very easy to choose - for most.

I am a fine artist, and I like to print up to 40 inches, in black and white. There is no digital camera that comes close to my needs. I use an 8x10 camera and when I drum scan the image I have a 568 megapixel file. (24, 39, 50, mgpxls is no comparison.) I tried going down to 4x5 (and 6x7), I have a scanner that is exceptional, and should be able to make a file that equals an 8x10. It clearly doesn't. It isn't a matter of numbers. In my case its more a matter of film "real estate".

If print quality is important to you in your work, and you print larger than 15-20 inches on occasion, then film might be a good option.

I would say you might want to rent a top end digital camera for a day and see what it can do. Get a high end drum scan of the same image and compare, with your work in mind.

Lenny

Clement Apffel

13-Jan-2009, 14:48

Thanks all for sharing your experience / point of view.

Everyone here but me noticed the “slip of the tongue” I made about units in my first message. It is of course micrometers and not nanometers. The mix-up came from an article about interferential filters involving tons of light wavelength values I red just before starting the topic.
Whatever.

With 35mm lenses, you couldn't stop further down than f/16 either without getting diffraction issues. This is not different with FF DSLR bodys.

Good point. But what I red about digital diffraction quality fall-off often sounded like there is no image at all after diffraction limit aperture.
I wanted some feedback on this point from top-end digital users.

I just see the excellent results from my 1Ds III and that is enough. For me, with prints up to 1m large.

I definitely need to see such prints.

Regarding tiny pixels, I see a great interest in them since it gives a total freedom to the digital imaging software engineer to do as much pre-processing as thay can inside the camera, or inside the digital back before delivering the actual image file to the end user.

So on the contrary I'm expecting that zillions of tiny pixels will continue to be both a marketing gimmick for the years to come, and a blessing for software engineers. It will give them so much freedom in pre-processing, that the question of the optical diffcation cut-off frequency wil be more or less marginal.

I’m afraid I can’t share your enthusiasm on this point.
Or maybe I do not fully understand your point here.

Tiny pixels won’t give any freedom to pre-processing engineer. It will give them a lot of hard work… and for what result: An opaque and artificial enhancement of a poor quality native capture.
I can’t see any good in such system. But maybe I am too old-fashion on this.
Once again, it does not seem to aim optimal quality nor user best interests but just marketing matters.

I spoke with Schneider LF technical people, and it was their opinion that at 22 megapixels, one could use traditional LF lenses and not expect to gain that much by "upgrading" to the Digitar type lenses. (I'm thinking in particular of the Mamiya 22mp digital back.) They emphasized that a lot could be accomplished, size-wise and otherwise with a back like that. Above 22p, they recomended more sophisticated lenses.

So, given the expenses involved, this is the direction towards which I'm heading. 22mp can do quite a lot. It'll take a while, but at least I have a plan. While I found an older style Arca 6x9 camera for a reasonable price, I've recently run across a way I can adapt this back to my 4x5. Etc.

Thank you for sharing your discussion with Schneider technicians. I wasn’t aware of that statement.

My question here would be: why not spare a reasonable amount of money and buy a 1Ds III or D3 instead of that 22Mpx back you are speaking about?
I read you plan to use such a back on your current 4x5” camera or on a 6x9 arca.
But is it the only reason?

I hope there is a quality step between 22mpx 35mm digital cameras and 22mpx digital back. And I understand it is your bet here.
Moreover I imagine that you plan to use movements on such a digital back in order to optimize the sensor native file size instead of stretching 35mm cameras file with perspective tool on Photoshop (like A LOT of photographers do).

But what is the reality of quality question here?
How leaf or hasselblad hope to sell more 22mpx digital back at such prices when 20mpx 35mm cameras are currently buyable second-hand?

I am aware that I’m exaggerating a bit, but you got the idea.
I am curious to hear your point on that.

However, I think that the current D3X really is at the performance limit; to go further would have extremely low improvement in optical resolution (not file sizes). I really feel that with the Canon 1Ds Mark III and Nikon D3X, those companies need to concentrate more on improving colour and sensitivity, and give the uberMP race a rest for a while.

Anyone else having this “deja vu” feeling?
Some years ago I clearly remember specialized journalists making that statement after the latest Kodak-fuji-canon-nikon-whoever 35mm digital camera release.
But the mpx race is still here.

Here too, I exaggerate. I am aware that there is a big quality step between two years old DSLRs and currents.
But the strange feeling I have about quality not being the main concern of producers still lingers on after those years. And I don’t see it stop tomorrow.

Strange how people see things differently. I also have a 1DsmkIII, I'm sort of disappointed with it, not that it does not perform very well, it does mostly. It leaves me thinking it should be better, hence a return to LF for me for the fun side of photography. The more pixels I have in 35mm cameras the more I like film. I've not found any Canon lenses to get me excited either. The latest range of pixel packed 35mm just leave me cold, all those pixels help highlight digital faults and make me realise how good film is and how I took it for granted.

Maybe that is close to the “strange feeling” I just spoke about.
Most of the DSLRs I tryed made that impression to me: “it should be better”
Those image screaming “DIGITAL”.
Those chromatic aberrations.
This poor dynamic range. Etc…

And very often for work, there is no time, clients want tons of images so they can have the illusion of choice, they want everything immediately.
So disappointing.
The quality doesn’t seem to be the main concern here either. Except maybe in fine art photography, but that’s another world.
As you say film is for the “fun side of photography” the side we keep for ourselves.

That sounds like a young professional photographer discovering the market of commercial photography. Actually that sounds correctly because that is exactly what it is. :)

Since I know from 35mm film experience that I can't get traditional near-to-far landscape compositions in full focus at f/8 (and frequently not even at f/11), it would seem that to achieve optimal landscape resolution with a 20+MP DSLR kit, I'd be limited to three tilt/shift lens focal lengths (with limited coverage compared to their LF film counterparts); above and beyond that, I'd have to shoot planar or limited depth-of-field subjects. A lot of folks are perfectly happy shooting 4x5 film with just three lenses (90, 150, and 240 are roughly comparable to the DSLR tilt/shift focal lengths), but I'm not. And stitching is of limited appeal since most of my subjects involve moving objects.

So it would seem that 35mm DSLR's can intrinsically achieve some LF film landscape photography objectives, but not all.

This is very interesting.
So why SO MANY professional keep buying DSLRs with PCE lenses? If it is that hardly limited?
Only because they are lazy to carry a large format gear or a tripod?
Only to spare few k $?

I mean the Nikon d3x is worth 8000$!
1Ds III 7000$ or so!
PC-E optics between 1500 and 2000$!
The total gear kit is in the 11k – 14k range!

When you can find used H3D-II at 16k on EBay!

Here too, I can sense I lack some field reality experience.

I use an 8x10 camera and when I drum scan the image I have a 568 megapixel file. (24, 39, 50, mgpxls is no comparison.).

Just a little technical comment here: I often read those comparisons between sheet film drum scan files and digital back files.
What is ignored to serve the superiority of film is that your drum scanner scans the grain. So that is not 568 Mpx of plain detail. To me the comparison is hedged.
If a scanner could deliver a 1000 Mpx of the same sheet of film would you announce that you have a 1Gpx details? 2 times more detail than you have on your current 568mpx files?
Of course not. The detail cap of film is way under those values. But the thing is we are so used to see grain enlarged that we do not consider it as a lack of detail.

But in the other hand, we do scream “unacceptable” on the minor little jpeg artefact on digital enlargements. It is both cultural and subjective.

Even though I plainly agree with you that an 8x10 is above current digital quality at same print size.
I'm not saying digital backs could achieve what you achieve with your drum scanned 8x10".
Just making it clear because I don't want a digital vs film war in this topic.
Just wanted to point that to me, such comparisons are wierd.

I think there are a lot of numbers out there. Some of them mean something and some of them don't. For commercial work, the convenience of digital and the small target size (magazine page) make it very easy to choose - for most.

[…]

If print quality is important to you in your work, and you print larger than 15-20 inches on occasion, then film might be a good option.

Yes, that is an excellent point. All this has to be related to the print size and the print technology used.
A photographer working for daily newspapers can jump into digital with a 5 years-old DSLR and still having caped quality for his print size / offset quality prints.

But actually, if I start such a topic, it is because I need to deliver files for up to 2.5m large (close to 100 inches) prints. And at digital speed: meaning very short amount of time.
Unfortunately film isn’t always doable. And my quality exigency forbids me to use a stretched 35mm digital file.

And that is the point of that thread: a top-end digital quality solution.

regards,
CA.

D. Bryant

13-Jan-2009, 15:16

Yes, that is an excellent point. All this has to be related to the print size and the print technology used.
A photographer working for daily newspapers can jump into digital with a 5 years-old DSLR and still having caped quality for his print size / offset quality prints.

CA.

The flaw with your conclusion here is that images that used to be targeted for printed media are passé. News papers, large and small, are dropping like flies, at least here in the USA. Staffs have been slashed to the bone and the survival schemes for traditional printed news outlets have been to position their daily publication for output to the web, though they are still trying to understand how to monetize this form of publishing. This increases their need for DSLRS that can transmit files directly to a PC for more or less instant uploads to the editing desk. The old days of photo journalism are over by and large and so are the old technologies and tools.

Don Bryant

bglick

13-Jan-2009, 16:23

> I spoke with Schneider LF technical people, and it was their opinion that at 22 megapixels, one could use traditional LF lenses and not expect to gain that much by "upgrading" to the Digitar type lenses. (I'm thinking in particular of the Mamiya 22mp digital back.) They emphasized that a lot could be accomplished, size-wise and otherwise with a back like that. Above 22p, they recomended more sophisticated lenses.

IMO, this is excellent advise, and a VERY valid point. But it must be a MF sensor, not smaller 35mm as mentioned. However, keep in mind, that LF lenses will never deliver the resolution that the Digitar lenses will.... so you will still have gains with digitar lenses...specially if the subject has very little depth, in which case you will have big gains, as the Digitars are optimized in the 5.6 - 8 range, vs. LF lenses in the f16+ range (dependent on fl). These details can make a big difference, if your type work allows it... Of course the real value of the MF back on a view camera lens, is the ability to stitch... now, you have the best of both worlds, assuming the subject is cooperative.

> I've not found any Canon lenses to get me excited either.

IMO, the value of DSLR is FAST lenses. Try the 200mm f2.0 if you want to have some fun. You can produce images not possible with LF. However, if DOF is your gig, LF is still the cats meow.... and large DOF is the death sentence to DSLR...it will never be optimized for such. Instead, its sweet spot is ultra fast lenses which are diffraction limited.... only the best lenses today will make these highly dense sensors produce amazing imagery.

For some, it becomes cost effective to buy some really expensive digital set up, such as the 60MP MF back with digitar lenses....but you have to shooot a lotttt of film for this to be true. This is the beauty of LF IMO.... for a few dollars, you can match the output of a $80k digital set up....

> I use an 8x10 camera and when I drum scan the image I have a 568 megapixel file.

I don't mean to start a war.... and another poster above has already touched on this..... but a 568 MP scanned file is very deceiving to many readers. Your statement gives the illusion, you would need a 568 MP digital camera to match the image quality of your 8x10 scanned film.... I am sure this was not your intent, and there is a lot of variables to consider, so I won't comment on your unique application, but to put things in perspective for others..... I offer the following....using 1/R, If we consider diffraction limited lenses, at 100 lp/mm MTF for high resolving B&W film, at these f stops, the max. resolution of 8x10 film is...

f32 - 204 MP
f45 - 125 MP
f64 - 72 MP

And in the rare situation, where you can infinity focus at f22 - 468 MP

Of course, with 8x10 color film the numbers are significantly less...using 60 lp/mm MTF of the film...

f32 - 139 MP
f45 - 92 MP
f64 - 54 MP

f22 - 204 MP

For those interested..... 4x5 color film at 60 lp/mm

f16 - 58 MP
f22 - 44 MP
f32 - 30 MP
f45 - 20 MP

These MP values represent the IQ of the film, NOT the file size. Often, to squeeze every last drop of resolution from film, the scanner must over-scan to grab all the resolution, creating file sizes that are enormous...... this is normal in all forms of reproduction work... and can be classified as "inefficiency" when going to a 2nd generation image. This value can vary from 1.3x to 3x based on the quality of the scanner.

Anyway, the point is here, the "devil is in the details" when comparing digital vs. film.... there is no cut n dry comparisons.... unfortunately...

As for the theme of initial post.... IMO, the MP wars are hitting brick walls.... next it will be lens wars to gain the benefit of those smaller pixels. A perfect example is the 50d... unless I use a near diffraction limited f2 lens (shot wide open) on it (which only one or two even exist, certainly not the 85 1.2) .... I don't gain much final rez over the previous 8MP or 10MP sensors. This is a perfect example of how most MP's are becoming marketing MP's vs. useful MP's. This makes perfect sense, and it demonstrates that the only sensible move from here, is to enlarge the sensor size, then it can accommodate smaller apt. settings, to gain more final rez AND allow smaller apt. settings. This was the move Leica recently made....I wonder if Canon and Nikon might some day end up in this camp, with a new line-up of lenses of course....

As others have pointed out....the next big break in digital, is MF sized sensors in the 40 - 60MP size that are reasonably priced. It sure is a mystery if that will ever happen...but if it does, it will be lethal hit to film.

Lenny Eiger

13-Jan-2009, 18:09

>
> I use an 8x10 camera and when I drum scan the image I have a 568 megapixel file.
I don't mean to start a war.... and another poster above has already touched on this..... but a 568 MP scanned file is very deceiving to many readers. Your statement gives the illusion, you would need a 568 MP digital camera to match the image quality of your 8x10 scanned film.... I am sure this was not your intent, and there is a lot of variables to consider, so I won't comment on your unique application, but to put things in perspective for others.....

I don't want a war either, and you are correct, I did not intend to say that anyone needed anything at that size. I'm enjoying it, but that is different from need.

I think the most important point I wanted to make is to try it both ways. One can rent equipment, etc.

I do expect (and hope) that when the megapixels of excellent backs get between the 200 and 468 that I can retire my film camera. I wonder about this. I have learned more about film real estate this year than I care to know.

In the meantime, however, the 8x10 is performing fabulously. Personally, I am not that interested in sharpness. I am more interested in depth of field and very interested separation between the midtones. In this respect, the numbers mean little - or maybe the numbers I'd like are not being calculated anywhere and aren't available.

Lenny

bglick

13-Jan-2009, 19:39

> And in the rare situation, where you can infinity focus at f22 - 468 MP

Sorry, this was a typo.... f22 - 329 MP (not 468 MP)

Anyway, my point was, your 568 MP file is probably equiv. to 1/2 (or less) of this value, in "real world resolution"........ The pure pixel count of a scanned file, converted to MP's is vooodo math. Scanned files are bloated with inefficiency.

IMO, one of the most annoying issues I have with scanned film is this file size issue. With digital capture, you often produce file sizes half the the MegaBytes vs. scanned film, but yet, they both contain the same resolution. that's the reality of...

1st generation digital capture vs. 2nd generation scanned film, bummer...

Eric Leppanen

13-Jan-2009, 20:15

But actually, if I start such a topic, it is because I need to deliver files for up to 2.5m large (close to 100 inches) prints. And at digital speed: meaning very short amount of time...And my quality exigency forbids me to use a stretched 35mm digital file.Assuming you have already ruled out a digital scanning back, and any kind of film solution is too slow, then you really have very few options here.

I would suggest first determining what level of print resolution you can accept in terms of DPI. You can then calculate the required capture resolution in terms of megapixels. West Coast Imaging (one of the major fine art digital print labs here in the U.S.) assembled a print resolution chart correlating capture resolution with print output quality. There is of course a lot of subjectivity here, but they tried to accomodate the needs of what they call "the average photographer". Click on the following link, then click on "MegaPixel to Print Size Char":

http://www.westcoastimaging.com/wci/page/info/FAQ/faqprintlab.html

Using the baseline or midpoints in the resolution ranges they give, WCI defines levels of print quality as follows:

"Superb" 200 DPI
"Excellent" 175 DPI
"Better" 125 DPI
"Good" 90 DPI

Of course a lot of fine art folks here on this forum would be appalled at the idea of a 90 DPI print being considered "Good", but I think we've all seen mural sized enlargements made from a 6 megapixel camera such as a Nikon D70 which would seem serviceable to many folks (albeit rather pixelated).

Apply these print densities to an 80 x 100 inch print, and you would need the following capture resolutions:

"Superb" 16,000 x 20,000 = 320 megapixels
"Excellent" 14,000 x 17,500 = 245 megapixels
"Better" 10,000 x 12,500 = 125 megapixels
"Good" 7,200 x 9,000 = 65 megapixels

"Good" is equivalent to enlarging a D70 image to a 22 x 32 inch print size, which would be passable for certain commercial subjects but certainly not arty in any way.

If you settle for "Good", then theoretically the newly announced 60 megapixel Phase One P65+ can nearly achieve the required resolution in a single shot (56 megapixel backs from Leaf and Sinar are also options). But this product is not shipping yet, and would require an investment of $50K+ to purchase new (renting presumably would be the best option). If "Good" is unacceptable, or the P65+ is not a viable solution for you, then you'll have no choice but to stitch. If stitching is feasible, then there are a whole bunch of possible solutions to choose from.

dh003i

13-Jan-2009, 21:14

As others have pointed out....the next big break in digital, is MF sized sensors in the 40 - 60MP size that are reasonably priced. It sure is a mystery if that will ever happen...but if it does, it will be lethal hit to film.

Thank you for your informative post on LF resolution. But even if reasonably priced MF sensors 40 - 60 MP in size are produced, that wouldn't mean the end of large-format cameras, due to the possibility of movements. MF backs can of course be designed to accomodate this, but it doesn't seem to have happened much yet. One possibility would seem to be producing digital backs for LF cameras. I know I've read there's problems with this, but can't technology take care of it? (and also, couldn't the light recepticles be large on LF, due to the maximum actual resolution of LF film, thus not needing recepticles as small? this would also reduce noise).

I imagine large digital sensors, with large individual light sensors.

bglick

13-Jan-2009, 22:42

Eric, great post.... reverse engineering the problem is the most sensible approach. I viewed the WCI link, a few comments about the link, and your well constructed post...

1) It's interesting the chart shows 6x7 film exceeding 63 MP back. This is a BIG stretch.... I think WCI is also confused about scanned file size (MB's) vs. digital captures (MP's).

2) Obviously, there is a lot more to the equation than MP's, as the amount of "recorded" data is highly dependent on the lens quality, f stop used, DOF, pixel size, etc. etc. The resultant "recorded resolutions" can vary by a factor of ~ 3x. So by no means is such a chart to be relied on. But for the avg. photographer, the chart is a good starting point to get a grip on how much resolution the captured image might contain, and how he can use this to evaluate print sizes.

3) The big missing factor, regarding the 100" print the OP has requested.... is viewing distance. A normal viewing distance is equal to a prints diagonal dimension. In which case, if you can make a print in the SUPERB range, at 16 x 20" (as an example), than each time you double the print size, you double the viewing distance. The perceived resolution will still be in the SUPERB category. This is why a Billboard can look tack sharp, even though the image was shot on 35mm film, as the image size from your viewing distance is the same as viewing a 4"x6" drug store print at arms length. When print becomes 100" long, I think it foolish to worry about close inspection, as you must be ~ 150" (13 ft diag.) away from the print to take the print in (visually). This "diagonal viewing distance" represents approx. a 55 deg FOV (Field of View), a very comfortable viewing angle for humans.

A viewing distance of half the print diagonal will produce a 110 deg. FOV. A human has approx. a 100 deg. stereoscopic FOV without moving the eyes or head. So I would suggest the viewing distance should be somewhere between the print diag., or if you really push the resolution envelope, than 1/2 the print diag. Any closer than half the print diag. the person can not see the entire print without scanning their eyes / head.

This provides a more realistic representation for the starting point of "how much capture resolution" is required for a print with a known diagonal. The numbers above are based on prints with aspect ratios of Square (1:1), to 1.25 : 1 (4x5). Adjust accordingly for different aspect ratio prints.

> One possibility would seem to be producing digital backs for LF cameras. I know I've read there's problems with this, but can't technology take care of it? (and also, couldn't the light recepticles be large on LF, due to the maximum actual resolution of LF film, thus not needing recepticles as small? this would also reduce noise).

MF backs already work with view cameras.... often with smaller view cameras that are higher precisioned for digital work... such as the Linhof 6x9, Toyo, Sinar, etc. You get the benefits of movements, if the lens has a big enough image circle, which will surely be limiting, at best. Many of these backs can also be retrofitted to fit 4x5 cameras, IIRC, many already have adapter plates for 4x5. I doubt they will make a digital back the size of 4x5, which I think was your question.....the reason is.... you will have to use longer fl lenses, which require higher f stops, limiting the potential resolution.... Anything is possible, but considering stitching is an option today (by moving the back around the image circle), it only leaves a single application for what you describe, non-static scenes. In which case, the single shot 60MP MF back comes close enough to 4x5...and who knows what next years MP will be? So I can't see any motive for such a product...but it sure would be nice....

This is pure speculation, but if high resolution photography follows the lead of high rez astro photography, where resolution is REALLY at a premium.... then possibly the next generation of high rez still photography will consist of combining 4 digital sensors into one back. There will be 4 lenses, one for each sensor - all capture a different part of the scene and automatically stitched together as one output file. The shutters will be LCD shutters built into the lenses, so sync will be perfect, as its all electronic. An LCD shutter would appear like an lens element, it will produce no aberations. With power applied to the LCD glass, it will block light, or allow it to pass through, just as a mechanical shutter does. The value here is, since its electricity, the response times are ultra fast. This is required for accurate sync. These shutters are in use today, mostly for studio photography where fast shutter speeds are not used.

The benefits are, you can still have large clean pixel sizes, high resolution, AND very fast, and very sharp lenses (due to their shorter fl's), even when DOF is required. Think of this as, "auto stitch". So this puts 100 - 150 MP into reality, with NO new advances in digital sensors.... considering Sony sells a 24MP camera body for $3k, the sensor can't be more than half this.... as you can see the possibilities are there. The missing link is.... a camera maker flushed with cash to R&D such a project. I think this is out of the scope of the Canons and Nikons market, so unless its a Leica, Zeiss Hassy or Phase One, I doubt we will see it. The real kicker is the LCD shutters, while they are fast and reliable, they are still a bit slow, IIRC, only 1/125 th max. shutter speed, and they draw a decent amount of power...but they are at their embryonic stage of development. A better solution is the sensor acting as the shutter..several companies are working on this now....then mechanical shutters will be history. Back to earth.....

dh003i

14-Jan-2009, 06:04

If the sensor acts as a shutter, then theoretically, each pixel could act as a shutter; you could have an HDR image quite easily.

rvhalejr

14-Jan-2009, 09:28

If the sensor acts as a shutter, then theoretically, each pixel could act as a shutter; you could have an HDR image quite easily.

I'm in love with the S5, I think they use two photo-sites for each pixel to get good HDR with "unsurpassed color fidelity". Any thoughts about that design ?

rvhalejr

14-Jan-2009, 10:34

> With digital capture, you often produce file sizes half the the MegaBytes vs. scanned film, but yet, they both contain the same resolution.

Do you see any value in comparing the two by ever shooting cy/mm targets and comparing results ?

rvhalejr

14-Jan-2009, 10:39

> .. The pure pixel count of a scanned file, converted to MP's is vooodo math...

SOoo... You have proved this because the Signal to Noise Ratio of both confirms this ?

bglick

14-Jan-2009, 10:48

> If the sensor acts as a shutter, then theoretically, each pixel could act as a shutter; you could have an HDR image quite easily.

Yes, this is theorecticaly true, although I am not sure its being worked on.... but it would be a joy if the pixels all accepted light for x period of time, eliminating the need for a shutter.

I never used the s5... I never heard of it classified as HDR... maybe a stop more of light? The design is excellent for color fidelity as you mention, its shortcoming is resolution. A major tradeoff...the market seems to prefer more resolution.

> Do you see any value in comparing the two by ever shooting cy/mm targets and comparing results ?

yes I have, this is what I am basing my comments on.... of course, the scanner variable is a big one....

> SOoo... You have proved this because the Signal to Noise Ratio of both confirms this ?

I don't think S/N ratio is an accurate description...but yes, it has been proven over and over....and falls under the same Nyquist principles I mentioned in your other thread. Its called over-sampling.... which creates inefficiency. There is a slew of other variables that also determines how inefficient the scan file will be vs. the first generation image.

rvhalejr

14-Jan-2009, 11:13

> IMO, the MP wars are hitting brick walls.

Amen. :) We still have Color Fidelity, Dynamic Range and how to decouple diffusion from resolution, etc.

By the way, your MP values for c41 seem rather high given the amount grain (noise)
I seem to get when its quantified on the computer in PS. Hmmm .,.

Bye the Bye you all familiar with how to quantify grain/noise as opposed to signal (image detail) ? No math involved and only takes a few minutes, be happy to detail the procedure if you do not recall.

rvhalejr

14-Jan-2009, 11:29

> I never used the s5... I never heard of it classified as HDR... maybe a stop more of light?

If I recall the S3 was said to have a really big photo-site to resolve shadows and a little photo-site to resolve highlights, combining both into one pixel. Simple design but very effective, two taking on the workload of one :)

rvhalejr

14-Jan-2009, 11:59

Posted by bglick
> .. The pure pixel count of a scanned file, converted to MP's is vooodo math...
Reply#1 by rvhalejr
>> SOoo... You have proved this because the Signal to Noise Ratio of both confirms this
Reply#2 by bglick
>>> I don't think S/N ratio is an accurate description..

Digital Electronic fundamentals are far from being vooodo math...

There cannot be any meaningful objective digital comparisons unless S/N is taken into account.

bglick

14-Jan-2009, 15:38

>>> I don't think S/N ratio is an accurate description..

Digital Electronic fundamentals are far from being vooodo math...

There cannot be any meaningful objective digital comparisons unless S/N is taken into account.

Rich, you are mis-applying my comment. S/N ratio is a component of scanning film. However, the reason the scanned file is so much larger than its digital capture cousin, is due to many other MORE significant factors. Such as optics, lighting, mechanical movement, object sizes on film, as well as the Nyquist principle of over-sampling. If you re-read what i wrote, I suggested that converting a scanned file MB's into MP's is voodoo math....there is NO sensible relationship between the MB's of a scanned file and MP's of a digital captured file. Many people mistakenly promote this fallacy.

Instead of creating a NASA level project from these comparisons, its easier to view through a microscope what your film can resolve...that's the true resolution, and represents the MP's of IQ the film contains. (very general statement, as resolution can vary across film)....

the IQ MP's / MP's converted from scanned MB's , represents the scanner efficiency. It will range from 25% - 90%. I can't fathom why anyone in the photography world would need to dissect each component of the over-all scanner efficiency value..?

Got it?

Lenny Eiger

14-Jan-2009, 15:57

>
f22 - 329 MP
f32 - 204 MP
f45 - 125 MP
f64 - 72 MP

OK, so I reviewed this - and I understand some of the logic you use, but I have to admit it makes no sense to me in real life. I recently did a test of the same image shot from f 22 to f 64. The only difference I can see is in depth of field. The sharp areas are very sharp in each one. If I read the above correctly, the f22 ought to be really superb as far as detail (at least where it is sharp) and the f64 ought to be about 1/4 the resolution - and 1/4 the file the other is. They are both very good.

This is where I have trouble - the numbers don't match my experience. This might be true in a tabletop situation, I couldn't say, haven't tested it. But outside in the daylight the f64 version is not 1/4 the file that the f22 is.. There is lots of data everywhere. I have scoured these negs and the resulting scans.

I am using a Nikon 300 on my Canham, developing the Efke 25 in D-23, stock.

I'm not trying to be argumentative. I just don't see it.

Lenny

dh003i

14-Jan-2009, 16:58

OK, so I reviewed this - and I understand some of the logic you use, but I have to admit it makes no sense to me in real life. I recently did a test of the same image shot from f 22 to f 64. The only difference I can see is in depth of field. The sharp areas are very sharp in each one. If I read the above correctly, the f22 ought to be really superb as far as detail (at least where it is sharp) and the f64 ought to be about 1/4 the resolution - and 1/4 the file the other is. They are both very good.

This is where I have trouble - the numbers don't match my experience. This might be true in a tabletop situation, I couldn't say, haven't tested it. But outside in the daylight the f64 version is not 1/4 the file that the f22 is.. There is lots of data everywhere. I have scoured these negs and the resulting scans.

I am using a Nikon 300 on my Canham, developing the Efke 25 in D-23, stock.

I'm not trying to be argumentative. I just don't see it.

Lenny

It could be that the f/22 images are not focused properly, as f/22 is less forgiving than f/64. Hence, they look to be of equivalent sharpness in the sharpest areas, but that's because your focusing is slightly off and f/22 thus doesn't seem any different than f/64 in the sharpest areas?

Bruce Watson

14-Jan-2009, 17:17

Lenny Eiger

14-Jan-2009, 17:34

It could be that the f/22 images are not focused properly, as f/22 is less forgiving than f/64. Hence, they look to be of equivalent sharpness in the sharpest areas, but that's because your focusing is slightly off and f/22 thus doesn't seem any different than f/64 in the sharpest areas?

I focused on a car tire. I can see the little parallel ribs on the sidewall and the text. There are some minor differences - some places where one is sharper than the other, so the focus may be slightly off, but there are areas fully focussed in both of them and they both look good, and both look good overall, plenty of detail, plenty of fully rendered pixels, etc. The real deal for me is that one image is not great and the other crap, or if not crap, just poor.... or 1/4 as good.

This leads me to the conclusion that, as with many numbers, they are theoretical. Imacon is famous for claiming that they have a DMAx of 4.8, which is beyond the maximum density of film. What did they use to test? Aluminum foil? When I complained about this, and referenced independent tests that show it has a DMax around 3.0-3.1, another person on the Scan list pointed out how they came to that number. It was a theoretical extrapolation of what the scanner "could" do.

I understand resolution, lines per mm and a lot of things around this issue. However, i have a 8x10 image, scanned at 2000 ppi I am looking at that is just over 300 mgpxels (16000 x 20000), about 500 megs of B&W and I don't see how it relates to being only 1/3 usable pixels. It isn't that shredded, not by a long shot. The f22 vs f64 does not display a huge difference, one to the other, in terms of quality. It's minor.

Lenny

Ron Marshall

14-Jan-2009, 18:55

I agree with what is stated below (although I haven't checked the numbers), diffraction does degrade image quality (just look at a pinhole image for an extreme example).

But don't forget, the image produced by a lens in front of a digital is also degraded by diffraction.

I offer the following....using 1/R, If we consider diffraction limited lenses, at 100 lp/mm MTF for high resolving B&W film, at these f stops, the max. resolution of 8x10 film is...

f32 - 204 MP
f45 - 125 MP
f64 - 72 MP

And in the rare situation, where you can infinity focus at f22 - 468 MP

Of course, with 8x10 color film the numbers are significantly less...using 60 lp/mm MTF of the film...

f32 - 139 MP
f45 - 92 MP
f64 - 54 MP

f22 - 204 MP

For those interested..... 4x5 color film at 60 lp/mm

f16 - 58 MP
f22 - 44 MP
f32 - 30 MP
f45 - 20 MP

bglick

14-Jan-2009, 20:08

> OK, so I reviewed this - and I understand some of the logic you use, but I have to admit it makes no sense to me in real life.

It will soon.... remember, the f #'s and their MP's are MAX. POSSIBLE recorded resolutions, not min. resolutions. This also represents the resolution at the POF (Point of exact Focus). So this assumes you are shooting a FLAT test target or an infinity scene, both having a flat focal plane. When you introduce depth into the equation, the near and far points will always have less resolution than the POF, (up to a point) so the f# and MP's values I offered above, you can cut them by 20 - 50% (estimate) based on the amount of depth you have in a scene. This is why the 568 MP values are so far from reality.... real world depth MP values for 8x10 at f45 can be in the 40 - 90 MP range, based on the amount of depth and f stop used. (more on this below) There has been several web examples of 40 MP digital captures nearly matching 8x10 film - same composure being compared...(color, not B&W) .... and when there is enough depth in the scene the gap can be surprisingly small...but shoot infinity subjects or FLAT subjects, and 8x10 film will destroy a 40 or 60 MP back. This is why the comparisons are all over the map... the devil is always in the details....

Also, as per my f# vs. MP values above, ..... in the real world, nothing is perfect, so these values are not fully attainable even with FLAT subjects such as test targets....but with enough precision, the right lenses, used at the right f stops, optimum subject contrast, optimum subject sizes, precise processing, etc., in theory they are attainable ....

Film records contrast....the finer the subject detail, the less contrast the lens will deliver, and the less detail the film can record. This is why you must combine the MTF of the lens and the film, and why they are both dependent on image frequency (amount of detail) Just look at the MTF curve of a lens, at high enough resolutions, their ability to deliver clean contrast to the film, goes right in the dumper. Bruce mentioned a perfect example, pine needles at a distance.... low contrast and very fine detail, in most cases, 1/R will turn these needles to mush on film... sad, but it's reality. It's the nature of imaging, not just film, same true with digital. But digital has the benefit of lower f stops, due to more dense recording media. This is films Achilles heel. Anyway, this is why there is some generalizations when making these "ballpark" judgements. In most cases, its to get us in the ballpark... unless you really want to get down to the sheer nitty gritty stuff...

> I recently did a test of the same image shot from f 22 to f 64. The only difference I can see is in depth of field. The sharp areas are very sharp in each one. If I read the above correctly, the f22 ought to be really superb as far as detail (at least where it is sharp) and the f64 ought to be about 1/4 the resolution - and 1/4 the file the other is. They are both very good.

As Bruce correctly mentioned .... at the POF (Point of Focus), f22 should yield a sharper image than f64. However, if the subject at the POF does not have enough detail, then it will "appear" equally sharp. The difference is, at f22, if you put finer detailed subject at the POF, then you will see how the MTF of the lens and film will yield a sharper image at f22. This where the nitty gritty comes into play. Just imagine a single metal column at the point of exact focus.... no detail....shoot at f22 and f64, it would be hard to tell the difference in the processed film....at best you will see tiny differences at the edges under high magnification. Now put a Pine Tree at the POF, you will see the difference very handily.... Of course, this is just at the POF....at the near / far points, as you suggest will vary greatly based on f stop.

> This is where I have trouble - the numbers don't match my experience.

This is because you are not applying all the variables to the equation. This is the value of performing tests with targets, it removes the subjectivity of saying, "they all look good"... with targets, you see where the cut-off is at each f stop and camera to subject distance. When done right, I can assure you after years of testing, the reality of recording detail is very predictable. But I will agree, it can be tricky for the newb... lots of variables within the optical principles and lots of variables in the particulars of specific lenses, films, etc. Again, the goal is not to nail results to within 5%....the goal is to prevent us from being off by 500%.... and thinking we are right... that's what the math is for... it steers you in the right direction for a specific task.

> I'm not trying to be argumentative. I just don't see it.

I understand you are not being argumentative...no problem. I hope my explanations helps you understand why "you don't see it" .... shoot test targets, and you will discover the basic math is remarkably accurate.

> This leads me to the conclusion that, as with many numbers, they are theoretical. Imacon is famous for claiming that they have a DMAx of 4.8, which is beyond the maximum density of film.

When doing a test, you need subjective information and must understand all the variables. From what I am reading, that does not seem to be the case here... the math is not "theoretical" it's been proven science for 50+ years. It's easy to be fooled by a test, then assume the math is faulty. I would not compare sound science like this (with no monetary motive behind the science) with Imacons marketing claims of x dpi or y Dmax. We know manufacturers exaggerate, stretch the truth, deceive, etc. to help sell products. This is a weak analogy.

> However, i have a 8x10 image, scanned at 2000 ppi I am looking at that is just over 300 mgpxels (16000 x 20000), about 500 megs of B&W and I don't see how it relates to being only 1/3 usable pixels.

The mistake you make is.... you assume the dpi you scan at - dictates the amount of resolution a given piece of film contains. You have the tail wagging the dog. The amount of resolution film contains is determined during imaging, not during scanning. I have seen you mention this several times. Here is a simple example that hopefully will bring these numbers into reality.....

We shoot a flat target at f45 with 8x10 color film with 60 lp/mm MTF at the given contrast value of the target. We assume perfect film alignment, focus and diffraction limited lens at f45, single focal plane.... OK?

AT best, we can resolve:

1/(1/33+1/60) = 21 lp/mm

(1500/45 = 33 lp/mm aerial rez)

This means a 30 lp/mm target at the film plane will NOT be resolvable under magnification...it will appear as a blob, vs. cleanly defined lines. It means 20 lp/mm target on the film will appear barely discernible....not a blob, but not sharp. A 10 lp/mm target will look sharp, and a 5 lp/mm target will look razor sharp. This is MTF at work... the finer the detail, the less contrast that is Transfered (hence the T, in MTF) This testing procedure is as old as the hills.... no voodoo math here.

Now, how much "usable resolution" does that 8x10 film have? The film has nothing resolvable over 21 lp/mm.... so it's resolution is stated as 21 lp/mm. Keep in mind, it might have areas of much less resolution, but 21 lp/mm represents the max. recorded resolution.

But since we want MP's, we must consider the film area.

21 * 2 = 42 lines per mm (not pairs)
lines in X Y axis are analogous to pixel

8x10 film is 200 x 250mm

or 10,714 * 8,571 = 91 MP

So 91 MP is the total amount of resolvable information in that 8x10 piece of processed film. No scanning is required to determine this... only a good film loupe, microscope and some simple math. It does not matter how deep you scan that film, there can not be more useful information than 91 MP. The scanner, AT BEST, will only extract the useful information in the film, it will NOT create new information. Hence why there is NO relationship between the size of your scanned files and the useful MP's in the film. Larger scanned files are due to the inefficiency of the scanner, which includes all the variables I mentioned in my previous post. Make sense now?

End of Part I

bglick

14-Jan-2009, 20:09

Part II

As a side note.... this 91 MP would be reduced to 57 MP, if we used f64 instead of f45...sad, huh.... Also, the 91 MP value would be be lessened by shooting a scene with depth, as the near and far points will not resolve as high as the POF. But that's another can of worms. Hopefully now, you can see how these recordable resolution values are not in the 586 MP range, determined by reverse calculating the MB's of a scanned file. Again, the best analogy for that practice is the "tail wagging the dog." You approached the equation from the wrong end.

For a quickie digital comparison, the f stop used, the depth and the pixel count are all variables that must be considered. But in keeping with normal f stop ranges for each format, as a general rule, using these smaller format sizes, which enable shorter fl lenses, hence lower f stops, a digital capture will produce 50 - 75% of recordable MP's, vs. their MP value. So a 60MP back can produce resolvable MP's in the 30 - 45 MP range. But these good digital backs have the ability to uprez very well, which will add some useful MP's back. The range accounts for color of targets, f stop used, lens type used, grid pattern of subject (sag. vs. tang.) etc. etc.

As you can see from this, its very feasible the new 60MP backs will match 8x10 color film (or come damn close) when 8x10 requires f64 to accommodate the depth in a scene. But 8x10 in B&W and / or infinity focus will blow away the 60MP backs.

Before digital, there was no reason to level the playing field between the two recording medias, so we only referred to resolution in lp/mm. But since MP's are all the rage today, everyone wants apples to apples comparisons between the two, so we are forced to convert OFR (On Film Resolution) lp/mm - into MP's, vs., MP's into lp/mm. IMO, the real benefit of this method is..... using MP's of recorded resolution accounts for the "area" issue between all the varying size sensors....it also levels the sensor density, film MTF's, lens MTF's, f stops, etc.

bglick

14-Jan-2009, 20:15

> But don't forget, the image produced by a lens in front of a digital is also degraded by diffraction.

Agreed Ron, we cross posted..... you will see this is accounted for in my digital values...much easier to equate MP of digital capture as 50 - 75% of the native pixel count, which takes many factors into account, not just 1/R.

Also, for your MP values, they represent the true MP values for flat subjects or infinity focus.... for depth, these MP values depreciate significantly...

rvhalejr

14-Jan-2009, 20:58

...
rvhalejr> There cannot be any meaningful objective digital comparisons unless S/N is taken into account...
bglick>>I don't think S/N ratio is an accurate description...
Rich, you are mis-applying my comment.

Sorry, just an old bit-kicker trying to drill down and attenuate the noise floor .,.

S/N ratio is a component of scanning film. However, the reason the scanned file is so much larger than its digital capture cousin, is due to many other MORE significant factors. Such as optics, lighting, mechanical movement, object sizes on film, as well as the Nyquist principle of over-sampling.
Yes, and scanning backs have similar internals and fair comparisons could be made with those (to both work flows). Perhaps he biggest difference between film and the digital back work flow is the initial high IQ (and high S/N ratio) as a result of its direct measurement and the proprietary software/firmware being run inside the digital back (on the SOCs, ASICS, FPGAs, etc.).

It may have been mentioned as of late that they may have started using optical cut-off filters for frequencies above the devices photo-site spatial limit (sub Nyquist diffusion filters). This might be considered the photo-site array equivalent of using fluid in the film scanning process (brick wall noise reduction without losing very little, if any, image detail i.e. signal). It would seem capable of attenuating noise, spurious resolution, aliasing etc.

Why not let the digital back processing cycles be equivalent to the fluid scan post-processing software steps on the desktop, they both reduce noise, both interpolate, up sample, sharpen and so-on :p

If you re-read what i wrote, I suggested that converting a scanned file MB's into MP's is voodoo math....there is NO sensible relationship between the MB's of a scanned file and MP's of a digital captured file.

Ok, I'm no on-the-metal chip expert, but some bit kickers/firmware/software engineers might have a slightly different perspective (as I will try to explain soon).

Many people mistakenly promote this fallacy.

Ouch! MB's of a film scanned file have a MOUNTIAN of noise, fluid can be used to attenuate grain (noise) quite nicely. Then MBs need processing through a suite of desktop software to get anywhere close to the digital IQ output (and hopefully stay on a level playing field). :p

Instead of creating a NASA level project from these comparisons,

Comparisons between the work-flows can be fast and simple (arguably over simplified here, ignoring gamma, standard deviation of the noise distribution, etc.).

To illustrate one might look at the image levels distribution curve in PS after selecting a 100x100 pixel square of blue sky (store a screen snap on the side).

Pick another square 100x100 square next to it, strong Gaussian blur the second square, look at the image levels distribution curve and you should have nothing but image data (ideally perfect with very little noise or grain).

Compare the two, S/N all done :p

its easier to view through a microscope what your film can resolve...that's the true resolution, and represents the MP's of IQ the film contains. (very general statement, as resolution can vary across film)....

GAG !!! Away bad Microscope, Away !!! (Otherwise it all looks like highway blacktop with your nose pressed against it). There is very little film IQ until (in PS on the desktop) noise is eliminated at the level just below the least detectable piece of an image under high zoom, then (as a minimum) down sampled and slightly sharpened.

If done right it becomes very difficult to determine what work-flow the image came from, but I'm old, so maybe not.,.

... the IQ MP's / MP's converted from scanned MB's , represents the scanner efficiency. It will range from 25% - 90%.
I can't fathom why anyone in the photography world would need to dissect each component of the over-all scanner efficiency value..?

Amen. :)

Got it?

A little DSP here, a little DSP there and pretty soon it all may have a fairly similar IQ (I've neglected white balance, color drift, etc.) at least for old people (without a 35x loupe) .,.

Perhaps, if one allows for a level playing field (heavy post fluid film scan processing in exchange for the backs equally powerful interpolation, noise reduction, sharpening firmware, etc.) a useful educated comparison might be made.,.

bglick

14-Jan-2009, 23:53

> Why not let the digital back processing cycles be equivalent to the fluid scan post-processing software steps on the desktop, they both reduce noise, both interpolate, up sample, sharpen and so-on

These comparisons do not consider post processing...if they did, digital would gain a further edge. It's the nature of processing, cleaner pixels up rez better.... when you toss this mix into the comparison, you can often add an additional 10 - 15% of the recorded MP of the digital capture...... just an estimate of up rez digital has.

In most of your posts you mention fluid scans. Most people on this forum doing high rez scans all fluid mount. So it's always assumed, vs. a new insight to squeeze more resolution from film. But regardless, the comparison always assumes the scanner retrieved 100% of the recorded resolution from the film.

> There is very little film IQ until (in PS on the desktop) noise is eliminated at the level just below the least detectable piece of an image under high zoom, then (as a minimum) down sampled and slightly sharpened.

This is true of both digital and film.... sharpening digital files is an integral part of the work flow, it's not really an option. But I would not suggest there is very little IQ in film, as 10 - 15x darkroom enlargements were the norm for years... of course, no digital manipulation then... that is a LOT of IQ ....

> Perhaps, if one allows for a level playing field (heavy post fluid film scan processing in exchange for the backs equally powerful interpolation, noise reduction, sharpening firmware, etc.) a useful educated comparison might be made.,.

This "IS" the comparison being made, today and the past 10 years now....... Once again Rich, as I mentioned many times in your other thread, fluid mounting, digital processing of the scanned film is all considered "normal" work-flows....its not the new breakthrough that you continue to suggest. So what you refer to as an "educated comparison" is exactly what has been discussed in this thread. As mentioned, if you kick up digital a bit for its edge in up rez, it simply closes the above gap a bit more... not enough to rock the comparison. I am trying to give film a fighting chance :-)

neil poulsen

15-Jan-2009, 04:19

. . . Thank you for sharing your discussion with Schneider technicians. I wasn’t aware of that statement.

My question here would be: why not spare a reasonable amount of money and buy a 1Ds III or D3 instead of that 22Mpx back you are speaking about?
I read you plan to use such a back on your current 4x5” camera or on a 6x9 arca.
But is it the only reason?

I hope there is a quality step between 22mpx 35mm digital cameras and 22mpx digital back. And I understand it is your bet here.
Moreover I imagine that you plan to use movements on such a digital back in order to optimize the sensor native file size instead of stretching 35mm cameras file with perspective tool on Photoshop (like A LOT of photographers do).

But what is the reality of quality question here?
How leaf or hasselblad hope to sell more 22mpx digital back at such prices when 20mpx 35mm cameras are currently buyable second-hand?

I am aware that I’m exaggerating a bit, but you got the idea.
I am curious to hear your point on that. . . .
CA.

Hi. This has been an excellent thread.

There are three reasons:

>> I want the movements that a digital back on a view camera can offer.

>> I regard a 35mm DSLR chamber as small, and light bounces around in there. The flare from an image with overcast sky, or in snow, etc., is PAINFULLY obvious. It's really awful. A digital back on a view camera can deal with this.

>> I've concluded from my Kodak SLR/c that has a full-frame sensor that the color integrity is better than on other DSLR cameras. My camera does not have an anti-aliasing filter, which is the same case with digital backs. Almost all other DSLR cameras have anti-aliasing filters. The only other exception of which I'm aware is the Leica M8. I find this very interesting, given Leica's preoccupation with producing a quality image. On this point, I've not myself done a side-by-side comparision. I draw my conclusions from people who have done these comparisons.

I might add that a second advantage of not having an anti-aliasing filter is improved resolution. Of course, not having the aa filter leaves one open to moire, which can be a real problem for some images. But, not so much for landscape.

------------------------

To add a little context to my comments, I do all all my photographing on a tripod. I rarely photograph handheld, DSLR or otherwise. So, I don't need the speed that a DSLR can offer.

Stefan Lungu

15-Jan-2009, 07:56

Strange how people see things differently. I also have a 1DsmkIII, I'm sort of disappointed with it, not that it does not perform very well, it does mostly. It leaves me thinking it should be better, hence a return to LF for me for the fun side of photography. The more pixels I have in 35mm cameras the more I like film. I've not found any Canon lenses to get me excited either. The latest range of pixel packed 35mm just leave me cold, all those pixels help highlight digital faults and make me realise how good film is and how I took it for granted.

Kevin.

Now, I don't think getting the 1Ds MKIII is not a good idea, unless you have the lenses to serve that fully packed sensor. So a dedicated photographer like yourself will be disappointed with most of Canons lens offering. But the talk here made me think : I started using a Canon 300D, 6Mp sensor. Now, to be able to double the frame length, I need four times more pixels, and that would be around the new 1Ds MkIII or 5d MkII. That is a hell of a leap in years and price, not to mention the lenses that looked "ok" or "good" on that sensor compared to how they would look like on the 20+MP sensors. I think a lot of the problems come from this never ending pixel race that brings nothing but trouble to the end user : artefacts from the noise reduction that has to be bigger with the smaller pixels, larger files and better lenses that are needed to get something right on that sensor.

bglick

15-Jan-2009, 11:31

> I think a lot of the problems come from this never ending pixel race that brings nothing but trouble to the end user : artefacts from the noise reduction that has to be bigger with the smaller pixels, larger files and better lenses that are needed to get something right on that sensor.

This is soooo true, well said..... its like Pandoras box. :-) However, part of the discussion here addresses this.... don't let the pixels get too small, by increasing the size of the sensors...you still need good lenses, a step better than most LF lenses, but its a very good solution... the deterrent is only price, such as the $40k P65, 60MP backs. The big question is, will these ever become reasonably priced?

HD Tv's were $15k in 1997, today, $1k.... We have all become accustomed to these technology price drops...even Sony at $3k for 24MP is setting new price bars. Whether this happens with larger, lower volume sensors...who knows... my guess is, the volume is just too low to ever get the price reductions that will make MF backs more mainstream.

rvhalejr

15-Jan-2009, 14:25

> as I mentioned many times in your other thread, fluid mounting, digital processing of the scanned film is all considered "normal" work-flows....its not the new breakthrough that you continue to suggest.

I cannot recall ever thinking that a fluid scan might be considered a breakthrough.

That word was once used in reference to a possible breakthrough coming soon[1].

When fluid scanning has been spelled out it has been for clarification, not intended to be overly redundant. I'm surprised that anyone would be annoyed by its use.

I would find it very interesting if you were to kick off a public discussion at some point about what you seem to refer to as "scanning at depth" in film.

I could be wrong but that sounds like your referring to the scanning the discrete color layers within the emulsion. Yes, that is an over simplified statement by design.

> I am trying to give film a fighting chance :-)

And so am I .,.

[1.] Hence research into one facet of fluid scanning that very well may prove fruitless, but those details might be better discussed off line .,.

bglick

15-Jan-2009, 15:35

> I would find it very interesting if you were to kick off a public discussion at some point about what you seem to refer to as "scanning at depth" in film.

I simply meant, scanning at greater ppi.... this is often referred to as a "deeper" scan, meaning, trying to extract more resolution. The Depth of Field of scanning lenses will not allow focus on each level of color within the film.

rvhalejr

16-Jan-2009, 07:52

bglick

16-Jan-2009, 14:56

Lenny, I was reading your marketing material on your web site....

320 MP for scanned 4x5 film... ???

YIKES!

SergeyT

16-Jan-2009, 18:42

>> For those interested..... 4x5 color film at 60 lp/mm
>> f16 - 58 MP
>> f22 - 44 MP
>> f32 - 30 MP
>> f45 - 20 MP

It was hard to me to believe into the numbers at first.
Then I remembered that I have two pictures of the same landscape to compare
- a 4x5 picture taken with a 300mm NikkorM at F32 on Delta 100 , wet-mount scanned at an optical scanners resolution of 2450 ppi with no sharpening.
- a 1Ds 11MP (with weakest AA filter among all Canon digital line) an EF 135F2L at F8 ISO100 in RAW. This picture covers less of the landscape area so I think it is appropriate for a rough comparison. The goal is to see if a 4x5 @ F32 "is" a 30 MP from a Digital sensor :)

The 4x5 scan came out to be 12000x10000.
The RAW converted into TIFF with no sharpening ~5000x3000
I up sampled the Canon's file in PS (bicubic sharper) for 4x to make it have 10000 along the longest side and finally to have the elements of landscape of the same size as on the 4x5 scanned image.
I gave some amount of USM to both files to make them both look the best.
Then I compared side by side the similar pieces of them at 100% magnification.

I was shocked to learn that the up-sampled Canon's file (on the screen) subjectively contained the same amount of details as the scanned 4x5. I think partly due to the virtual absence of the grain and noise in Canon's capture. Well I had to add about 5% of noise (a PS filter) to the Canon's file to make it look "closer" to the scanned 4x5. Otherwise I could not stand the grain on 4x5 :)

So the 4x5 >> f32 - 30 MP sounds like the right number.

bglick

16-Jan-2009, 19:08

dh003i

17-Jan-2009, 09:24

> So the 4x5 >> f32 - 30 MP sounds like the right number.

30 MP? Some will argue it should be 320 MP ? Oh what the heck, it's only a difference of 10x. ;-)

Anyway, it's nice to see "some" sanity offered to the digital vs. film issue.

And you are sooo right.... digital's up rez capacity is mind boggling.... of course, the cleaner the pixels, the better the up-rez capacity, hence the value of these larger pixels. If you up-rez a digital capture 2x, its impressive how well it holds up...and at this 2x size, ~ 10% of the total pixels were actually recorded at capture.... 90% of the pixels are interpolated. If someone tried to convince me of this 10 years ago, I would tell them, they were insane.... it's a tough pill for many to swallow, even today.

I find it difficult to believe that the relatively tiny 35mm sensor on a "full-frame" digital SLR can match the final print quality of a 4x5 image, even when used at high f-stops. Didn't you post a graph showing that prints made from 4x5 had higher lp/mm's than thoe from 35mm, even at higher f-stops (although the advantage deteriorated).

See this test of 4x5 vs. the MF P45 back, (http://www.luminous-landscape.com/essays/Cramer.shtml) where 4x5 still has a (slight) advantage over the best new MF back. Granted, this is a relatively flat subject, and I don't see info about the f-stop used for those pics. But it doesn't look to me like the P45 file can be up-rez'ed particularly better than the 4x5 file. It looks like it is maybe smoother with pure color tones (see the color chart, where film's grain shows), but that it has less detail in other areas. Which would, imo, make it a wash versus the 4x5 file for upscaling. (we can't consider the color, as the author told us there was still something funky going on with P45 color calibration).

And that's for a P45 back, not a 35mm digital. I find it difficult to believe that 35mm digitals can produce images with as much stunning detail as this (http://www.widerange.org/gallery.php?gallery=resolution). The latest 4x5 vs. P45 results seem to show the P45 being equal to 4x5 (http://www.outbackphoto.com/artofraw/raw_28/essay.html), according to the author. (look for the Rematch! P45 vs. 4x5 Velvia section). My impression is that for smoother color-tones and the leaves, the P45 outresolves 4x5 film, but for the connifer needles, the 4x5 out-resolves the P45.

In any event, for ordinary people, the P45 is certainly way way out of their price-range, and so too are Canon or Nikkon full-frame 35mm digital cameras.

PS: There is also some research (above my head), and experimental verification, of designing lenses that over-come the diffraction limit.

bglick

17-Jan-2009, 09:53

bglick

17-Jan-2009, 12:39

> There is also some research (above my head), and experimental verification, of designing lenses that over-come the diffraction limit.

Any links? their seems to be no method to overcome diffraction in ONE single apt. But the methods I read about being tested side-step diffraction, by using multi lens set ups, to capture different parts of the subject.... with this technique, you can use much shorter and therefore faster lenses, in the end, you have cheated the diffraction limits through by combining the images via sensor hardware / software. This will be a major boost to imaging....specially astro photography....not sure if it will filter down to still photography..

Gordon Moat

17-Jan-2009, 13:41

My . . . look at the time . . . where to start . . . So, one issue is on screen comparison, in that what you see on any computer monitor is a poor representation of printing capability. Such comparisons even reach an extreme of some people in public wondering why an image that looks so great on their HD television cannot make a good giant print. Now if your goal is only to display on monitors or giant televisions, then I fail to see why one would use film at all.

The Ludicrous Landscape comparisons have been discussed heavily in many past posts here, so . . . consider that these are aging baby boomers with eyesight not nearly as good as it was in the past. I think the level of acceptable comparison has reached the limits of eyesight for these individuals.

Simple aspects left untested: put an anti-alias filter onto a film camera, and place a grid pattern over the film. The idea is to turn the capture into discrete blocks of information. Then a later scan would allow these blocks to be more easily interpolated into an upscaled image. Sounds crazy? Yes, so here is the practical way to do that: view the film through a loupe, noting the detail information. Next use a high end digital back or DSLR to photograph the film. Break up the 4x5 piece of film until the capture is close enough to recording details visible through the loupe, sort of like doing a slide copy set-up. Then stitch the results until a large file is made that equals the film capture details as seen through the loupe. Last, count the megapixels.

Then there is the reality check. I have been vastly impressed at the quality of large prints from certain photographers, though the prints of Edward Burtynsky have impressed me the most. These were mostly in the range of 40" by 50", and from 4x5 film, some of them enlargements and others from a machine. Using 304.8 dpi at the 40" by 50" size, would give just over 185 MP, for those who want such numbers. However, I think a better number is the usual visual capability of the average viewer, which is often thought to be near 6 lp/mm, and oddly enough that relates well to 304.8 dpi . . . probably why that (or 300dpi) has been common printing industry specification for a long time already.

Sometimes the implied message is that it cannot be possible to make nice looking large prints from film, because digital capture is so much more advanced. Obviously this is not something anyone has directly stated in this manner, but when we apply such satire to these arguments, then I think it can allow us to be more objective. Any of us who has been to a gallery or museum and seen nice large prints already has one answer for themselves, and all they need to do is figure out whether they want to emulate the techniques and tools, or go their own direction. The prints of Edward Burtynsky impressed me enough that I bought back into large format three years ago.

Ciao!

Gordon Moat Photography (http://www.gordonmoat.com)

dh003i

17-Jan-2009, 13:48

> I find it difficult to believe that the relatively tiny 35mm sensor on a "full-frame" digital SLR can match the final print quality of a 4x5 image, even when used at high f-stops.

Clearly, 4x5 scanned film files will out perform 21 - 24 MP digital capture. Of course there is a lot of variables that can push the comparison further in one direction or another. In my previous posts, where I stated the recordable MP's of 4x5...as you can see, its more than 35mm digital.... even at f32 for 4x5, 30 MP... compare this with 21 MP DSLR * 65% (avg recordable rez factor) = 14 MP. At f16 for 4x5, as you can see, the recorded rez doubles to 58 MP.... this is a significant difference. Hence why the comparisons are so "variable dependent". DSLR's have the huge benefit of low f stops, due to their shorter fl's, so apt. diffraction is not so degrading. Not true for 4x5.

The up rez capability of digital capture varies greatly based on the pixels, technique, subject contrast, subject colors, etc. Sometimes the results are amazing, other times, just good...hence why I try to leave this variable out. The previous poster obviously had a great up rez experience in his comparison. I have had similar experience that just floor me.

The problem with up-rez'ing something is that you're just making up details. It may look ok, but that doesn't mean it has more detail. And if you say an "up-rez'ed" a digital capture picture by 4x, you also ought to up-rez a large-format film capture by 4x with the same settings, and then compare that. Now, I wouldn't be surprised if in some things, the digital up-rez's better, due to not having grain (but it does have its own noise problems, and imho, the noise on digital sensors is less appealing than grain noise). The $20k P45 is an exception, which didn't seem to have digital noise artifacts (I've seen demo units for $20k, now that the P65 is out).

I believe the site making the comparison noted that the costs of film will quickly add up for a 4x5 user, making the now-$20k P45 more affordable in the long-run for those who take many pictures. However, I don't know if he considered opportunity cost in that comparison; namely, there's about an $18k difference between comparable systems for P45 and 4x5 (and I'm not even including lenses for the P45). $18k would earn substantial amounts of interest. In short, you have to do a Net Present Value calculation to figure out which is more cost-effective.

The cost of the P45 is fairly obvious: $20k + lenses, all upfront cost. The cost of 4x5 is more complex. It of course includes the cost of the system + lenses (say $2000), then film ($2/sheet), plus the cost of scanning it. But you can't just add that up over the expected use-life of the 4x5, and say "oh, it's more expensive". You have to discount the costs by some opportunity-cost rate of return (say 6%, probably more), as such:

Net Present Cost = C1(1+r1) + C2(1+r2)^2 + ... = C[1 - (1+i)^-t]/i
where C1 = cost in year 1, C2 = cost in year 2, r = i = rate of return or interest rate, t = time, and C = annual cost, assuming the cost is the same every year.

(normally, we'd do "net present value", but it's difficult to quantify the value of having a camera system, although doable; but this isn't particularly relevant here if we assume the image quality of both systems is the same, so the Net Present Benefit will be the same, but Net Present Cost will be different)

The link you provided at the LL enforces the sensible MP values of scanned 4x5 film I provided previously. In this example, 4x5 scanned film just barely out resolved the 39 MP back... and this makes perfect sense with the imaging math above....

39 MP * 70% = 27 MP recorded resolution

vs.

4x5 scanned color film ranges from 30 - 58 "recorded" MP in the common f stop range.

So based on this, I would say the Charles Cramers test probably exposed the 4x5 at f22 or f32.... the resultant comparison makes perfect sense... no vooo dooo ...

More importantly, it demonstrates 4x5 scanned film is NOT 320 MP as some posters continue to endorse....and in another thread, I have seen numbers as high as 400 MP.

Well, 4x5 scanned film may be close to a useful resolution of 320 MP at wider apertures, if the lens is designed for that (i.e., Xenotar 135/3.5, which is sharp wide open and very sharp stopped down just a little). Of course, that is more useful for portraits and abstracts, not landscape (unless it lends itself particularly well to tilt).

But I agree, for normal subjects, where you have to stop down even with tilts, due to the various heights of objects you want in focus, 4x5 won't be 320 MP.

Also keep in mind, if the subject matter is static, you can stitch a handful of low end DSLR images together and easily surpass 4x5 IQ. This represents the lowest cost, and highest IQ possible....

Yes, but then that's also an argument against MF digital backs as well, and against full-frame sensors, or even APS-C. Then everyone should use the DSLR I have, the Oly E-3 (or maybe E-520, that's cheaper), with the 4/3rds sensor. With the 2x crop factor over 35mm, you can really peer far into the image with a 300/5.6 lens (equivalent to 600/11.2 in 35mm), and take an enormous capture. Although it would probably be better to use an uber-high-quality lens, like the Olympus Zuiko Digital ED 300/2.5 or Sigma Apo 300-800/5.6 EX DG HSM. Although those cost thousands of dollars, so could only be reneted for price-affordability.

Then you have to do many many shots, and sure you can get a 1 gigapixel image, or greater. But it takes quite a long time. And you can also do panoramic stitching with large-format 4x5 scans, although to get the same reach as a 300mm in 4/3rds, you'd need a 2,250mm large-format lens (a little bit excessive), unless you want to do wider format panoramas.

Also, some subjects may be static enough for LF 4x5, but not static enough for the repositioning necessary to stitch an image. Then, you [I]may need to do do focus-bracketing, to get the same effect as LF tilt. But looking at close-ups of LF scans vs. 1:1 of the output from my Oly E-3 (as much as I love it), I don't think that a 2 x 2 stitch (4 images total) from my E-3 will be as good as 1 large-format shot. Nor from other prosumer SLRs, like the Canons or Nikons.

Certainly, doing a 14 x 14 stitch with the E3 (assuming 10% overlap), that's 14 x 14 x 10Mp x 60% (due to overlap) = 1.176 Gigapixels. That will an incredible photo. IF the conditions were such that one had enough time to take it. I don't know if this can be done during photographic prime-time (sunsets, sunrises, dusk, dawn). This 1 gigapixel image took 13 minutes to photograph (http://www.tawbaware.com/maxlyons/gigapixel.htm). I can only imagine how long it took to photograph this 17 gigapixel image took to photograph (http://www.yosemite-17-gigapixels.com/) (presumably 17 times as long, so 3.7 hours).

dh003i

17-Jan-2009, 13:52

> There is also some research (above my head), and experimental verification, of designing lenses that over-come the diffraction limit.

Any links?

See this google search (http://http://www.google.com/search?num=100&hl=en&safe=off&client=firefox-a&rls=com.ubuntu%3Aen-US%3Aunofficial&hs=4MI&q=overcoming+diffraction+limits&btnG=Search).

Nathan Potter

17-Jan-2009, 13:58

This is an interesting and thought provoking thread for someone who has not thought rigorously about digital capture.

I'm wondering about how one would compare the contrast of the recording medium in film vs digital. All film and photosensitive media have contrast properties which at a basic physical level means that light spreads as it enters an emulsion and in fact the latent image can migrate laterally over time during and after exposure; and certainly during development. Thus the aerial image formed by the lens will be degraded when finally replicated in film.

I think the digital situation may be different though. Since each pixel is a discrete entity, once the aerial ray bundle is recorded by a pixel it stays in place. I'm beginning to think that one could show mathematically that the equivalent image contrast in the digital capture case could be somewhat superior to the film case; all other factors being equal of course.

Could this be why some workers are surprised by the quality of digital capture?

Nate Potter, Austin TX.

dh003i

17-Jan-2009, 14:16

by the way, some of this stuff might dilute the artistic value of pictures, as people start doing crazy things. The 17-gigapixel image I linked to seems well-composed. I think the key is to start out with a composition that you think is excellent to begin with (during a time of day when you have hours to make the pano). That's quite a bit different from just clicking away with maximum zoom in all directions.

Consider the Gigapan (http://www.gigapansystems.com/mm5/merchant.mvc?Screen=PROD&Store_Code=GS&Product_Code=I-B1&Category_Code=GPI). Great little machine, INCREDIBLE actually at current prices ($280). It's a robot that takes panos, so you don't have to do this. This is great, although I'm sure some would say it takes some of the "talent" out of doing panoramic shots (as if moving a camera precisely X degrees after every click is a talent).

But for photographic art, people may get the wrong idea (http://www.livescience.com/common/media/video/player.php?aid=20627). The last sentence is both technologically inspiring, but also could be misunderstood: "imagine a world with no pictures, just one big gigapan, or is it, terapan?" (the idea being that eventually, the entire world is photographed in one 3D navigational panoram?). Well, then, that's more like virtual reality, like actually going to the place. Different from photography.

bglick

17-Jan-2009, 14:47

> consider that these are aging baby boomers with eyesight not nearly as good as it was in the past. I think the level of acceptable comparison has reached the limits of eyesight for these individuals.

The players you are discussing are in their 50's. At this age range, what is lost is the eyes ability to accommodate, not resolve. Most people still have good resolution at this age. Hence the use of corrective eye wear to correct accommodation failure. In addition, when a print or screen view is enlarged enough, the eye is NEVER the limiting factor, even for 50 yr old dinosaur. So this position is completely invalid.

> view the film through a loupe, noting the detail information. Next use a high end digital back or DSLR to photograph the film. Break up the 4x5 piece of film until the capture is close enough to recording details visible through the loupe, sort of like doing a slide copy set-up. Then stitch the results until a large file is made that equals the film capture details as seen through the loupe. Last, count the megapixels.

If you followed this thread, and the other one running concurrently, this is nearly what I have described. Two clarifications. First, viewing test targets on the film, under optical magnification will provide the level of detail of recorded resolution, PERIOD! Next, the analog to digital conversion you propose, with a digital back....... this process has been perfected - hence why film scanners are used....which essentially perform the same stitch process you propose...but with all the proper hardware, software, firmware to extract all the data from film. Regardless of how big the file becomes, due to inefficiency of the scan process, the MP's were set via optical magnification of the film... from there, its assumed the scanner can extract the data, regardless of its efficiency. One of the difference between a great scanner a mediocre scanner is the final file size to extract all the films data. The lesser the quality the scanner, the more over sampling required, the bigger the file.

> Using 304.8 dpi at the 40" by 50" size, would give just over 185 MP, for those who want such numbers.

You are confusing dpi values sent to a printer, vs. recorded dpi on the film, or the sensor. They are never the same, due the eff. losses of analog to digital conversion and the losses of imaging itself, 1/R.

> However, I think a better number is the usual visual capability of the average viewer, which is often thought to be near 6 lp/mm, and oddly enough that relates well to 304.8 dpi . . . probably why that (or 300dpi) has been common printing industry specification for a long time already.

You are on the right track here...but you left out a significant factor in humans ability to resolve - distance. Human eye resolution is expressed in arc minutes, as it has no associated distance variable. 20/20 vision is considered the ability to resolve one arc minute, which equates to 6.8 lp/mm AT 250mm viewing distance (10 inches). This is considered the MOST the human eye can resolve, which is often young people with Great vision. A more realistic number for the general population is 3 - 5 lp/mm. Lets use 4 lp/mm.

I don't anyone who views relatively large prints at 10 inches... the avg. person over 35 can no longer focus at 10".... Considering we are discussing relatively large prints here, I would suggest using 25 inches. At this distance, our avg. eye can resolve 4 / 2.5 = 1.6 lp/mm. This would be classified as a very aggressive goal for large prints in the 20"+ range. A 430% difference vs. the 6.8 lp/mm you introduced. It's missing details such as this, that leads people to think 4x5 film contains 400 MP of recorded information....the devil is ALWAYS in the details.... and the details are off by HUGE factors in every facet of these discussions......

Anyway, the rest of you method of reverse engineering the amount of required resolution is fundamentally sound.

> Any of us who has been to a gallery or museum and seen nice large prints already has one answer for themselves, and all they need to do is figure out whether they want to emulate the techniques and tools, or go their own direction. The prints of Edward Burtynsky impressed me enough that I bought back into large format three years ago.

When you consider the viewing distance in galleries, its very common to be viewing at 4 ft or more (often 6 ft for large prints).... therefore, the print only needs to have 1/2 the 1.6 lp/mm stated above (for 4 ft, or 50"). At which point, more resolution in the print would NOT be resolvable by our visual system. There is many capture techniques capable of meeting these On Print Resolutions.

Interestingly enough, at 1.6 lp/mm, we are only using about 30% of an ink jet printers resolution capacity, which ranges from 3 lp/mm to 9 lp/mm based on the quality of the print heads, printer and paper type.... of course the glossy papers hold the most resolution. This also assumes sufficient resolution is sent to the printer.

From this point, more "perceived" resolution is added by lighting, as the contrast of the print increases, we perceive the image as being sharper.... hence the perfect lighting in galleries, it's a "play" on our visual system. One walk into a Peter Lik gallery, you will see this effect. Adding significant brightness to a print, to the point of driving down your eye pupil to 3 - 3.5mm in diameter, vs. an avg 5mm diam. pupil for indoor viewing conditions, will almost double the perceived resolution. The eyes MTF curve is highly dependent on pupil diameter. But that's another can of worms...

> Sometimes the implied message is that it cannot be possible to make nice looking large prints from film, because digital capture is so much more advanced.

I certainly NEVER implied this, and I do not think many have here either....whats being discussed is the relative differences between the two capture techniques...

bglick

17-Jan-2009, 15:24

> The problem with up-rez'ing something is that you're just making up details. It may look ok, but that doesn't mean it has more detail.

The advent of digital has created a means to add edge sharpness, remove grain / noise and add contrast, etc. These attributes of an image, contribute significantly to our ability to sense sharpness, resolution, acuity.... its a mixed bag. As we improve these attributes, the improved image can be enlarged a more as a result. The point is, digital manipulation can add many of the features that a slightly better lens "would" would have produced at capture. While you can do the same with a film file, the outcome is often not as effective, due to the file not being as clean... damn film grain :-) You can call it what you want... it's pretty amazing... as mentioned previously, 10 years ago, I could have never imagining technology available for peanuts, to perform like this. The process is so good, I have made prints from digital captures, in which the final file size represented ~ 85 % interpolated pixels.... and from the proper viewing distance, they are as sharp as any 8x10 film capture I have made. Of course, at these print sizes, the eye is the limiting factor. At 100" print sizes, the game changes...

I do agree with your assessment that there is limits to all this...it's not a limitless venture. But when you start adding in things like stitching a few images, well the rules change again.... this is why I keep stating, there is a host of variables to consider.... but the outcomes are more predictable than most think, once they digest all the application of all the variables.

As for your cost basis, digital vs. film.... nothing will be more cost effective than LF film and a used drum scanner if you don't shoot a ton of film.... for pros shooting tons of film, they probably converted long ago....also, remember, not everyone basis their decisions on payback.... many people just consider this a hobby, and if funds permit, they buy the toyz...

> But I agree, for normal subjects, where you have to stop down even with tilts, due to the various heights of objects you want in focus, 4x5 won't be 320 MP.

Or barely 1/10 th of 320 MP ! There is web sites promoting this...by seasoned pros. I do find it mis leading. I have nothing against film, I love it.... but at the same time, I am a realist.....

As for your position on the stitch DSLR, MF backs, stitching 4x5's, etc. etc. All valid points, I fully agree, but that's a pandoras box.... it's what every each can afford, whatever suits your working style, how much gear you are willing to lug around, learn to master, etc. Sometimes you need to walk from some shots, cause you are not set up to record them as you wish... such is life. And yes, I stitched a bunch of my Sigmonster APO 300-800 / 5.6.... and they are sweet.....but NOT as sweet as stitching shots from my Canon 200mm f2.0.... beyond spectacular. This lens generates near perfect MTF curves, mind boggling imagery... blows away my Digitars... but at 3x the price, nothing is free in this field.

As for the stitched shots at Max Lyons site, remember he was using a 8MP camera IIRC.... simply using a 24 MP Sony will cut the shot count significantly... and fast lenses would have been really helpful...but not every method of capture will meet every application, hence why there is so many photographic products.

> Thus the aerial image formed by the lens will be degraded when finally replicated in film.

Yep, hence why 1/R is an attempt to join the two MTF's to predict a final resolution.. Contrast is the MAJOR contributing factor to resolution. Lens MTF represents the amount of a targets contrast will be transfered by the lens, to the film at given distances, f stops and frequencies. Films MTF represents how much of that contrast will be recorded by the film at each frequency....

> I'm beginning to think that one could show mathematically that the equivalent image contrast in the digital capture case could be somewhat superior to the film case; all other factors being equal of course. Could this be why some workers are surprised by the quality of digital capture?

YES.... remember, the film MTF curves have done all the math for you... hence the MTF curve for each film. Sensors don't offer MTF curves, mainly, as you suggest, there is little if any " analog bleed" like film has, as light is reflecting not just where a light ray lands, but also around surrounding areas as its reflected. Bayer sensor still has the weak link of having less R and B pixels vs. G. This is another thread though.... :-)

dh003i

17-Jan-2009, 16:01

bglick,

Your points are valid...I guess that right now, looking at it from my pov, I consider a combination of my Oly E-3 and large-format setup to offer the best value (highest performance/price ratio).

One other thing is of course the advantage of tilts in large-format. If the shot is such that, with tilts, at f/22 or below, you can get everything in focus, it seems like a huge advantage there over smaller formats (say 10MP)...where to get the same kind or resolution, you'd need 4 - 6 shots, and then to get that sharpness throughout, you'd need focus-bracketing (so maybe multiply that times 3).

bglick

17-Jan-2009, 16:15

Gigapan is very cool...but its for digiams? Seitz makes one as well, which will handle heavy lenses....but I passed at $2500, since it only captures X axis...so only horizontal pans, bummer. Had it would have been an XY device, I would have jumped in....

> by the way, some of this stuff might dilute the artistic value of pictures, as people start doing crazy things.

Were just discussing tools of the trades....some are physical, some are mental.... what you do with the all the tools in your toobox, determines your art. I work under the premise, more knowledge is never worse.... not "always" better though...

dh003i

17-Jan-2009, 16:29

Gigapan is very cool...but its for digiams? Seitz makes one as well, which will handle heavy lenses....but I passed at $2500, since it only captures X axis...so only horizontal pans, bummer. Had it would have been an XY device, I would have jumped in....

I think someone has used it with an Oly E-510 or E-500 (http://www.fredmiranda.com/forum/topic/675132), although there may be issues. They are working on a version designed for the needs of DSLR cams.

bglick

17-Jan-2009, 16:31

IF the new version can handle big lenses, it will be a winner.....
heck, they can justify a lot $ for it, assuming it works as advertised...

very nice tool !

dh003i

17-Jan-2009, 16:40

IF the new version can handle big lenses, it will be a winner.....
heck, they can justify a lot $ for it, assuming it works as advertised...

very nice tool !

Even for an E500 or E510 (I hope it works on my heavier E3), with only lenses less than 100mm, I nominate them for Sainthood for selling it for only $280!

Gordon Moat

17-Jan-2009, 17:51

Due to your quoting method, it is very difficult to respond, so bear with me as I attempt this.

The players you are discussing are in their 50's. At this age range, what is lost is the eyes ability to accommodate, not resolve. Most people still have good resolution at this age. Hence the use of corrective eye wear to correct accommodation failure. In addition, when a print or screen view is enlarged enough, the eye is NEVER the limiting factor, even for 50 yr old dinosaur. So this position is completely invalid.

I am reminded of Claude Monet painting ever larger images as his eyes lost their ability to accommodate.
:cool:

Quite simply, if you enlarged an image to the size of a barn, some people would still be unable to tell you whether it was good, or whether it really was better than some other image that they hoped to compare.

Simple question: are younger eyes (in general) more capable than older eyes?

I saw Charles Cramer's prints on display not long after the LL comparison. I was not the only person who saw those that found no marked improvement of his prints when comparing film origination to digital back captures. If there was a technical improvement, then his printers became the weak link in his image chain and failed to show the improvements. This is not to state that his images were inferior, because I think he shows some compelling scenes, and they are generally good to great technically.

If you followed this thread, and the other one running concurrently, this is nearly what I have described. Two clarifications. First, viewing test targets on the film, under optical magnification will provide the level of detail of recorded resolution, PERIOD!

I fail to see your reason for such emphasis. Too often those who mention test targets fail to consider real world usage, while the opposite is that real world images are poor choices of resolution testing. Then there are others who choose to state contrast differences to attempt quantifying one method over another. Really, we could go in endless circles with this crap. Let's pick one method, and stick to it; I'll let you decide, since you seem less flexible in this.
;)

Next, the analog to digital conversion you propose, with a digital back....... this process has been perfected - hence why film scanners are used....

Obviously film scanners, but I should restate my objective with this. One capture device is used for the scene (or test target, if you prefer). Then the film is processed, and a DSLR or MFDB is used to re-photograph the film. A loupe is used to view details on the film. Then PhotoShop is used to see details in the captured file. In other words, if a 39MP digital back is equal to Fuji Astia 100F on 4x5, then one shot should be needed for the MFDB to capture every bit of detail on the 4x5 film. I really think this is simple. If the DSLR or MFDB cannot capture all detail in one shot, then two, four, or more shots could be taken, results stitched, and comparison made. Then we could state that 39MP=4x5 or 78MP=4x5, or some other measure. This eliminates the MFDB to scanner comparison that shows up too often in comparisons. I don't consider this as an alternative to a scanner; this is only a test; scanning film is more practical than using this as a commercial photography work practice.

You are confusing dpi values sent to a printer, vs. recorded dpi on the film, or the sensor. They are never the same, due the eff. losses of analog to digital conversion and the losses of imaging itself, 1/R.

I am not confusing shit . . . but we need to settle upon a method of comparison. I think it is so obvious that a pixel does not equal a dot. I think it is also obvious that all pixels are not the same dimensions. Even all dots are not the same dimensions across printing methods, papers, and inks (due to dot gain, and other factors). In commercial printing, there is variable dot size, stochastic printing, frequency modulation printing, line screens, screenless printing, and variable dot placement. In commercial printing we print out colour bars and registration targets, though we could add a Siemens star or perhaps even some test targets. So what would be helpful would be to suggest a method that is easy to reproduce and valid for comparison, rather than stating the obvious and then suggesting nothing. I will admit my ignorance of not understanding WTF "1/R" means, but I hope you can suggest something constructive . . . and yes I have read this entire thread and the other thread.

Me: "However, I think a better number is the usual visual capability of the average viewer, which is often thought to be near 6 lp/mm, and oddly enough that relates well to 304.8 dpi . . . probably why that (or 300dpi) has been common printing industry specification for a long time already."

You are on the right track here...but you left out a significant factor in humans ability to resolve - distance. Human eye resolution is expressed in arc minutes, as it has no associated distance variable. 20/20 vision is considered the ability to resolve one arc minute, which equates to 6.8 lp/mm AT 250mm viewing distance (10 inches). This is considered the MOST the human eye can resolve, which is often young people with Great vision. A more realistic number for the general population is 3 - 5 lp/mm. Lets use 4 lp/mm.

I have seen numbers from 3 lp/mm to 10 lp/mm, depending upon author. If you want to use 4 lp/mm, then that's fine, but I tend to stick with practices common in commercial printing. There is no right or wrong here as I see it, but if you want to think you are more right, then I'll play along.
:cool:

I don't anyone who views relatively large prints at 10 inches... the avg. person over 35 can no longer focus at 10".... Considering we are discussing relatively large prints here, I would suggest using 25 inches. At this distance, our avg. eye can resolve 4 / 2.5 = 1.6 lp/mm. This would be classified as a very aggressive goal for large prints in the 20"+ range. A 430% difference vs. the 6.8 lp/mm you introduced. It's missing details such as this, that leads people to think 4x5 film contains 400 MP of recorded information....the devil is ALWAYS in the details.... and the details are off by HUGE factors in every facet of these discussions......

Anyway, the rest of you method of reverse engineering the amount of required resolution is fundamentally sound.

So that brings us back to my test suggestion. Someone out there with access to one of the latest MFDBs, a Canon 1Ds Mark III, or a Nikon D3X, should just give it a try. Obviously a not top of the line lens could alter the results, but I think it would be valid with a good sample of a readily available lens.

When you consider the viewing distance in galleries, its very common to be viewing at 4 ft or more (often 6 ft for large prints).... therefore, the print only needs to have 1/2 the 1.6 lp/mm stated above (for 4 ft, or 50"). At which point, more resolution in the print would NOT be resolvable by our visual system. There is many capture techniques capable of meeting these On Print Resolutions. ... Interestingly enough, at 1.6 lp/mm, we are only using about 30% of an ink jet printers resolution capacity, which ranges from 3 lp/mm to 9 lp/mm based on the quality of the print heads, printer and paper type.... of course the glossy papers hold the most resolution. This also assumes sufficient resolution is sent to the printer.

I fail to be impressed by the majority of inkjet prints I see, for several reasons, though I understand it is quite popular. The Burtynsky prints I saw were continuous tone chemical RA-4 prints, and not inkjet. That was at MOPA, and I was able to go right up to the prints to view the details. So there was no four feet away for me on this, and I was not the only person there doing so. Not long after I was those images, MOPA had an exhibit of the GigaPXL Project, and they gave out magnifying glasses to anyone who wanted a closer look. Obviously those were inkjet prints. Using a magnifying glass was the same as using a printers loupe when checking a print run; it was more obvious that the GigaPXL prints were not continuous tone. Anyway, I suppose if I simply stood back and viewed the images, that I would have seen less detail. The images of Edward Burtynsky, particularly those of mines, compelled many museum visitors to go in closer for a look at the details. I encourage anyone to actually see an exhibit of his in person, prior to making a judgment on the technical limitations of 4x5 films and RA-4 prints.

Me: "Sometimes the implied message is that it cannot be possible to make nice looking large prints from film, because digital capture is so much more advanced."
:D

I certainly NEVER implied this, and I do not think many have here either....whats being discussed is the relative differences between the two capture techniques...

Apples cannot equal mangoes, yet we want to quantify these things. I see too many claims one way or the other, almost to the point that meaningful comparison disappears. When someone states that there is no way 4x5 film is XX megapixels, than that is an opinion, and has yet to be born out in reality, despite numerous attempts to accomplish that. Let's assume you claim 4x5 film is XX MegaPixels; okay then, prove it to me by showing me, and not with the same tired comparisons others have done.

Ciao!

Gordon Moat Photography (http://www.gordonmoat.com)

P.S. - I am limited in how many cute smileys I can include. Please consider much of this posting to be at times satyrical.

Eric Leppanen

17-Jan-2009, 18:59

There is currently a related thread over at the GetDPI forum, started by Marc Andrew Williams (a professional photographer who shoots multiple film and digital formats and has been heavily involved with MF digital). His opening comments:

First off, as most of you know...I embraced digital immediately, and have sunk a King's ransom into it ... heck, some of you got into digital capture, even MF digital capture at my urging...

So, here's the thing:

I personally do not think ANY digital photography has equalled film capture ... and I seriously fear that it never will (at least in my lifetime). Now I'm not talking about the usual caveats like B&W looks better to some people, I think it's across the board. I'm talking about looking at images the way they were intended ... as a visual medium viewed the way a human being looks at pictures, rather than using the the criteria of pixel peeping @ 200% on a computer screen, 100% side-by-side crops, or sterile resolution comparisons.

Each year I review all my work and add my best few to a collection I keep. Each time I review the total collection, in every case the film works not only look better in general, they specifically look natively sharper, have more feeling of detail and real depth, and are richer ... especially richer in the contrast while still holding detail across the tonal scale. I know all the intellectual technological arguments against this conclusion, and have read countless pieces of information that says I'm wrong ... (which of course I embrace because I have sunk that King's ransom into digital

My eyes tell me differently ... every time. Digital looks great ... until it's next to a well processed film shot ... even a scanned one.

(NO, I am not abandoning digital, just thinking out loud and wondering if I've bought into a set of new clothes that doesn't exist)

The responses he gets are generally pretty balanced assessments of film and digital capture, which are mostly viewed as coexisting technologies. This from a mostly digitally oriented group. The thread is located here: http://forum.getdpi.com/forum/showthread.php?t=4972

Interesting.

bglick

17-Jan-2009, 20:02

YIKES! This thread took a some serious "S" curves....

I will try to respond to a few of the "basics", as if we must agree with these, otherwise, we will never address the primary question you are pursuing..... which is...

> Let's assume you claim 4x5 film is XX MegaPixels; okay then, prove it to me by showing me, and not with the same tired comparisons others have done.

I am sorry my quote method confused you.... whenever you see ">", that means you wrote it. Where you do NOT see ">", that means I am writing it.... all those boxes take up too much space.....

First, we must see if there is a meeting of the minds of 1/R. You mentioned you had read the other threads.... but you don't know "WTF" 1/R is? I spelled it out previously, but will give the abbreviated definition again... its an imaging formula, used and accepted by Lieca, Zeiss, Kodak, Fuji, for over 50 years.... etc. etc. The Fuji handbook had a nice section on it, but I believe it's out of print. Regardless, its quite simple......

R = 1/(1/r1 + 1/r2)

R = Max. recorded resolution on the recording media.

r1 = Aerial resolution of lens

r2 = MTF of the recording media

For simplicity sake, all in the same units of measure, lp/mm.

The Aerial resolution of any lens can not exceed 1500 / f stop = lp/mm. (1500 represents the avg. wavelength of light, close enough for our needs)

The MTF of the recording media... if using a digital sensor, its simply how many pixel pairs per mm... if using film, you view the MTF chart of the film, at a given contrast ratio of a target, it provides you the max. lp/mm the film can record at a given frequency. You are a pro, so I am sure you have read film MTF charts through the years, so I won't go there....

Do the math, and R = the MAX. recordable resolution. This is extremely predictable...and it sets limits on "how much recorded resolution" is possible. I have tested lenses / film / digital for many years, and I can practically predict the outcome of every test I do. Now, if people on these forums suggest the result of this formula is off by a factor of 10x.... and your position is, they could be right, cause this is all about opinions, and all this whacko optical science that has been accepted religiously for 50+ years by all the optical engineers of the major imaging companies, ....then we may have to part company here. There is MANY resources you can read on this subject, and it's quite simple to test this yourself. Just get some test targets and fire away. You can see the 1/R numbers provided above in this thread and the other concurrent threads. So the ball is in your court on this one, fair enough?

I will touch briefly on a few more issues you raised..... not getting too deep, as we must pass step ONE above first.....

> Too often those who mention test targets fail to consider real world usage, Really, we could go in endless circles with this crap. Let's pick one method, and stick to it;

The problem with real world images is.....you don't know exactly what you are testing. Test targets eliminate this subjectivity... you can get most people to agree on what level target was resolved on film or on screen. When shooting real world images, you can easily be fooled by recording subjects with insufficient spatial frequencies to differentiate one system over another...an example is, the resultant outcome can be, THEY BOTH LOOK GREAT. That's not what we want to avoid when comparing two systems, we want to know how far each system can be pushed before differences become apparent. So IMO, there is ONLY one way to test, and thats using targets. Shooting scenes as many do is so hit or miss, it's sensless IMO.... its OK for fun or a quickie comparison, but no hard data can be learned. After the data is known, then shoot some scenes....

> Simple question: are younger eyes (in general) more capable than older eyes?

define older? Vision degrades with age.... but up to 40 - 50 years of age, the biggest degredation comes from lack of accommodation (inability to focus) which is correctable. Resolution falls a bit, but not extreme...till about 60, then its a downward spiral... of course, this is a generalization. A simple Snellen test will advise anyone of their resolution capacity.

> Then we could state that 39MP=4x5 or 78MP=4x5, or some other measure. This eliminates the MFDB to scanner comparison that shows up too often in comparisons.

You are over analyzing this.... or not fully understanding.... if you want to see how much resolution film resolved, all you need is a good loupe (of sufficient magnification) on a light box. The targets that are resolved will tell you the EXACT amount of recorded resolution on the film. There is NO need to scan the film, or take digital capture of the film. Your eye with a the right optic can't be beat. We already know a good scanner can grab all the detail in the film, thats been proven a zillion times. Once you know the resolution, you enter the "area" into the equation. Thats what this thread has been doing... max. recorded resolution * area = MP's. Pretty simple, and it brings the comparison down to apples to apples, not apples to mangos. The comparison all along has been, max. recorded MP's vs. max. recorded MP's.

> I have seen numbers from 3 lp/mm to 10 lp/mm, depending upon author. If you want to use 4 lp/mm, then that's fine, but I tend to stick with practices common in commercial printing.

The reason you see so many variances in the lp/mm values, is because it's commonplace to forget the distance factor, which is critical. The 4 lp/mm I suggested is at - the "closest distinct focus distance", a standard that has been used for 100+ years now, which is 250mm or 10 inches. This distance is also the basis for what we refer to as "magnification". A 50mm loupe, has 5x magnification, 250/50. It also is the basis of the Snellen chart, i.e. 20/20 vision, which was based on one arc minute of resolution, or 6 lp/mm. I think 4 lp/mm represents the general population much better, that was my only point. But every time you double the view distance, you reduce this value in half...to hold the same resolution. Or, if you want to hold that resolution on a 100" print at a 10" view distance, than you stick with 4 lp/mm...(not being sarcastic). It doesn't matter what you choose, as its nothing more than a variable in your formula to determine amount of resolution you are trying to capture to meet the goals of your final product. Make sense?

> Let's assume you claim 4x5 film is XX MegaPixels; okay then, prove it to me by showing me,

I suggest you prove it to yourself.... shoot some targets, you don't even need 4x5, use 35mm film, as at the f stops we are considering, f22 / f32 for example, both format lenses will likely be diffraction limited. If you need some targets, i suggest Edmunds, or you can get a nice color target from Charles Sleicher <charles@sleicher.net>... I think $35... I like his targets, as they are in RGB and B&W, ideal for digital capture testing.

Of course this testing has been done for years, its obvious the formula is accurate, you can not exceed the 1/R value.....and in our case, we are only dealing with Max. recordable resolution....cause we are not trying to nail 10% differences, instead, we are trying to debunk errors in the 10x range. Chris Perez has a slew of test results on this web site for 10 years now, they all obey 1/R.... (of course he has tested some real vintage lenses) but if you don't grasp the premise, or don't believe the fundamentals, join the wonderful world of resolution testing! OK by you ?

sgelb

17-Jan-2009, 23:19

digital will never have the feel of film. ever.

sgelb

17-Jan-2009, 23:21

also have a look at the tests made with the P65 or whatever the latest high end digital back.. magnified its pixelated and over sharp.. I hate it. looks garish.. ugh..

Steve M Hostetter

18-Jan-2009, 07:24

If you saw something you cut it,,, If you've "seen" something then you ,, well then you sound smarter... please continue

bglick

18-Jan-2009, 11:39

dh003....the google search you linked, is a bad link....any links to resources?

Gordon Moat

18-Jan-2009, 11:53

Regarding tests done by C. Perez, et al, a glance through the data shows about 60 lp/mm on 4x5 film for many lenses, with a few doing better than that. The comments surrounding those tests also indicates that shooting a more open aperture theoretically could improve the results, but at the expense of DOF. However, I think if we choose 60 lp/mm and the area of 4x5 film, then we have a reasonable figure.

Film holders vary a bit, though about 95mm by 120mm seems to cleanly cover those I have at hand. Using the 60 lp/mm figure, and 4x5 film captured area, roughly equates to 164 MegaPixels. Obviously, if technique was poor, a lens was slightly better or worse, film flatness was so-so, or various other factors, then that figure could be higher or lower.

http://www.phaseone.com/Content/p1digitalbacks/Pplusseries/Pplus/P65+.aspx

Interestingly, the near 6 µm pixel size is in an optimum range of size to noise, fill factor, and resolving capability in sensors, whether CCD or CMOS. The few tests that exist for sensors of near this 6 µm pixel size indicate resolving capabilities of about 50 lp/mm to 60 lp/mm. While I have not seen such of test of the PhaseOne P65+, if we used the 60 lp/mm figure, and the chip area of 40.4mm by 53.9mm, then one can see that the captured information is less than the file size and theoretical maximum suggest. This should be no surprise, due to the dead area between pixels, the Bayer pattern filter, and the IR cutoff filter (plus anti-alias filters and micro-lenses on Canon and Nikon chips). If every pixel could really capture a line, or a space, then the efficiency and capabilities would be as impressive as the file sizes suggest. I think this relates well to scanning, in that film is limited by the scanning device.

If we went about this in reverse, assuming 60.48 MP as our target for 4x5 film, to equal the best digital back on the market, then we could arrive at another figure. Using the file size of the PhaseOne P65+ of 6732 by 8984 and relating that to our film area of roughly 95mm by 120mm, we can see that the aspect ratio would require a slight crop for the film to match the chip (which more elongated). If we could get 36 lp/mm on the 4x5 film, then we could match the chip capability. However, due to some losses in scanning, we would need more than that in order to retain that much information in a scanned file. I don't think it is too much of a stretch, assuming a very good scanner and scanner operator, to see that the capability of the best MFDB currently on the market is within reach of many 4x5 users with access to good scanning.

Also, a big thank you for including that thread on GetDPI. While I have heard similar comments from some professionals, it is not often that it gets typed up and posted somewhere that others can easily access it. It might be of interest to know that some of the best paid professional advertising shooters are still using film, despite that their budgets would easily allow purchase, lease, or rental of the latest MFDB.

I am impressed at the capabilities of some MFDBs and the latest high end DSLRs from Nikon and Canon. I have yet to become unimpressed with the capabilities of film cameras, which is probably one reason why I still use film. The colour abilities are usually more important to me and my clients than the resolution, because they and I have never found the resolution of film to be an issue (so far).

I recently used a 1937 AGFA Jsolette 6x4.5, and an early 1950s AGFA/Ansco 6x9, to photograph some classic cars. A look at the results on transparency film without a loupe shows some quite nice images, which really was the only point of using these cameras for these shots. While not the latest lenses, the results hold up very nicely. The fun part was that using those old cameras allowed me a different level of access, because people made sure to give me room to get the shots I wanted. It was also a good conversation starter, and a great way to meet people. So this proves nothing about technology, other than I don't think all that one does in photography needs to be about technology.

Ciao!

Gordon Moat Photography (http://www.gordonmoat.com)

bglick

18-Jan-2009, 14:02

Gordon, it appears you made a "U" turn from your last thread....first, you were interested in the technicals, this thread you lost interest.... That's OK.... but,

your analysis of the Perez tests is at best, "partially" accurate".... and leaves out pertinent details, which is how all these resolution myths continue to harbor on these forums...

1) You suggest 60 lp/mm to 4x5 film - this ONLY a reasonable figure (as you suggest) if you use the same high Rez B&W film Perez used in the test. When comparing digital to film, as in this thread, it revolves around color capture. B&W film has a major advantage over color digital capture since the B&W films have nearly double the MTF as color films at similar contrast ratio targets. In which case, your 150 MP value of 4x5 recorded resolution is accurate, but ONLY at f 11. At more realistic f stop usage for DOF...

B&W
f22 = 88 MP
f32 = 49 MP

As you can see apt. diffraction is films worse nightmare....and often glossed over as an insignificant factor, as well as 1/R. The opposite is the reality of imaging.

2) If you correct the MTF for common color films, and use 60 lp/mm MTF for the film, we are back to:

f16 = 57 MP
f22 = 44 MP
f32 = 30 MP

So for color comparison, at more common f stops, your "generalized assumption" is about 300% exaggerated. details, details, details...

Next, your P65+ 60MP MF back comparison to 4x5....8984 x 6732 pixels at 53.9 x 40.4mm. 4x5 has 2.2x greater diag., it will therefore require 2.2x greater f stop for equivalent DOF. (or the P65 will require /2.2 f stop vs. 4x5) So the yield at equal DOF f stops would be...

f16 (4x5) = f 7.3 (P65+) = 31 MP

f22 (4x5) = f 10.0 (P65+) = 25 MP

f32 (4x5) = f 14.5 (P65+) = 19 MP

Based on these calc. 1/R values, 4x5 color film holds about 1.8x the recorded MP's. Which equals about a 34% increase in recorded resolution for 4x5 color film..... (because if you double the recorded resolution, you will 4x the recorded MP's.)

I did not compensate for differences in aspect ratio, as there is NO single desirable aspect ratio, so regardless of which format you have, you may have to crop to the other format. This represents the total recorded resolution for each sensors aspect ratio....people can alter them to their taste...

This 34% gain in "calculated" resolution is offset by the mix of the higher resolving lenses on MF AND the tremendous up rez capability of these large pixel sites..... hence why, the previous 40MP backs just fell short of scanned 4x5 film...and this current evolution of MFDB's will match scanned 4x5 color film.....but possibly scanned Velvia might hold a slight edge, but we are pulling hairs... Anyway, all the numbers make perfect sense vs. real world testing, and this will borne out as many more tests will be surfacing soon.

Again, this is not anti-film propaganda.... instead, its a means to draw apples to apples MP comparisons that make sense.... and to de-bunk these ludicrous 200 - 400 MP claims for scanned 4x5 color film.

While these P65 backs might be out of reach $ for the avg. person, the new crop of 24MP DSLR's are now a strong contender when a scene is static.... as the smaller format continues to benefit from less diffraction.... a few examples using 4000x6000 pixels for 24x36 for equal DOF. (.3 f stop, 43/150mm diag)

f16 (4x5) = f 4.8 DSLR = 15 MP
f22 (4x5) = f 6.6 DSLR = 13 MP
f32 (4x5) = f 9.6 DSLR = 10 MP

The power and cost effectiveness of these DSLR's is hard to deny.... Interestingly enough, they have the same pixel density as the new P65+. (~ 83 pp/mm) The DSLR sensors benefit from lower diffraction, so a few stitched shots can achieve amazing IQ, and is available to the masses - at least when the subjects are static. 1/R can be viewed as an efficiency equation, the lower the f stops, the more eff. the recorded resolution vs. the raw pixel count....

Averaging the three 60MP values above, avg. recorded efficiency is 42%

But for the 24MP DSLR, the avg. recorded efficiency is 54%...

this is VERY significant.... and represents why continued increases in sensor size and pixel count NEVER produces linear gains in recorded resolution. This is why stitching is sooo powerful, as the smaller sensors gain the benefits of less diffraction. So 2 - 3 stitched 24MP shots will get you equal to the $40k backs....IMO, this will cut deep into MF back sales, as their true differentiating feature is reduced to "non static" subjects. Considering the huge price differential between the new DSLR crop at 21 - 24 MP.... change is in the air. or... MF back makers will have to become more price competitive...

rvhalejr

18-Jan-2009, 14:17

I suggest you prove it to yourself.... shoot some targets, you don't even need 4x5, use 35mm film, as at the f stops we are considering, f22 / f32 for example, both format lenses will likely be diffraction limited. If you need some targets, i suggest Edmunds, or you can get a nice color target from Charles Sleicher <charles@sleicher.net>... I think $35... I like his targets, as they are in RGB and B&W, ideal for digital capture testing.

Consider this If you want to go beyond shooting a simple target.

I like chopping the big CS poster up into 4 square inch targets and placing them in three different positions (near, far, middle) to evaluate my newb tilt efforts. I will include the spatial dimensions as an approximation for calculating the cy/mm if it would save some from the pain of using a 100x microscope with reticule.

For another $35 you can get a 35-40x loupe, which after having used a lot would never want to be without (although its usefulness behind gg is often greatly diminished).

I also recommend testing the full range of useful f stops on any given lens. Its just that f32 and above require the use of lamps and a light stand or two.

For more serious work a Glass or Acrylic plenum is (arguably) a must. You can have these made yourself of buy some. For those fixated on precision (like myself) the plenums can be shimmed and entire system calibrated (if your into measurements) to whatever degree you would like.

I miss not having a group of people to share and contrast findings with and I do not care much for being one of a handful finding the optimal POF under any given condition.

Most here seem to think a 35x loupe is a waste time and feel its their duty to let you know about it. It would probably be better if one just enjoyed using it and did not make mention of it.

dh003i

18-Jan-2009, 14:45

dh003....the google search you linked, is a bad link....any links to resources?

Sure,

Superlenses to overcome the diffraction limits (http://www.nature.com/nmat/journal/v7/n6/full/nmat2141.html)

Overcoming the Diffraction Limit with a Planar Left-Handed transmission-line lens (http://http://www.ncbi.nlm.nih.gov/pubmed/15089166)

but also just google: overcoming diffraction limits OR limit

bglick

18-Jan-2009, 17:40

> Most here seem to think a 35x loupe is a waste time and feel its their duty to let you know about it.

Not sure who you are referring to, but I bet its me. If so, you have mis interpreted what I wrote. Sometimes I think 35x loupes is perfect for the application, other times the magnification is too great, and sometimes, you need 70x magnification, where I would consider 35x it insufficient. I am not knocking your tool Rich, I only suggest using the "right tool" for the right job....when 35x is the right tool, I use it. I use loupes from 2x to 125x. There is NO single loupe that is "best", and no loupe "is a waste of time" as you wrote above. A sledge hammer is not the right tool to hammer in a finishing nail? Clear?

bglick

18-Jan-2009, 17:51

I googled the diffraction limits....

Most everything relates to microscopic type optics....not photographic...

Microscopes and telescopes magnify an aerial image produced by the objective lenses...this is called a compound optic. This extreme magnification, often 200x or greater is why diffraction is always the limiting obstacle, as the goal is to always see more detail.

This is not true with photographic lenses... we are dealing with magnification values of .2 - 3x range.... so I doubt we will ever see anything overcome the apt. diffraction limits, certainly not in our lifetime...

Gordon Moat

18-Jan-2009, 18:06

First off, there is no tremendous upres potential that a digital sensor has over scanned film, and if you think there is then you don't know what the hell you are doing. I state this with 14 years of PhotoShop experience, because it has been possible to cleanly upsize smaller digital files (scanned film or capture), and with minimal noise, for quite some time; in the past it was more labor intensive, though now there are various software solutions that make it simpler and faster. Upscaling, no matter what software magic you throw at it, never increases resolution, it only increases file sizes. Anyway, I think that is all that needs to be stated on that. If you think otherwise, you are entitled to your opinion, and I will flatly disagree with you. I should mention that I have heard this too often, and it is one of the great misstatements about digital capture.

Fujifilm Astia 100F figures are 60 lp/mm at 1.6:1 and 140 lp/mm at 1000:1, while Kodak Tmax100 is 63 lp/mm at 1.6:1 and 200 lp/mm at 1000:1. Tmax400 actually performs worse than Fuji Astia 100F. So I don't quite get how you are claiming that B/W film is so much better than colour film. Even if I go with Fuji Velvia 50 that is 80 lp/mm at 1.6:1 and 160 lp/mm at 1000:1. None of these are exotic films.

http://www.fujifilm.com/products/professional_films/pdf/astia_100f_datasheet.pdf

http://www.kodak.com/global/en/professional/support/techPubs/f4016/f4016.pdf

http://www.fujifilm.com/products/professional_films/pdf/velvia_50_datasheet.pdf

It seems too much that you are pulling numbers to suite your own conclusions, and I am not seeing these backed up in reality. You make assumptions and then plug your assumed numbers in order to inflate your weak arguments. Your choices of using math is falling far short of convincing me of anything, so once again if you think any modern MFDB or DSLR equals 4x5 film, then re-photograph the 4x5 and prove it. The test is so simple.

Do I think a circa 24 MP capture equals 4x5 Fuji Astia 100F or Velvia 50? No, and I don't think I will ever see a large print that proves that, no matter what math you want to throw at it. I suggest you actually try to replicate what your math suggests, and then try to figure out why it simply doesn't work that way. This bench racing serves no purpose. If you believe so highly in your theories and number choices, then back up your claims, or choose a known photographer whom you think proves them, and I will find somewhere to view said individuals large prints.

The PhaseOne P65+ is only capturing around 30 MP of real information, despite that the file sizes are 60.4 MP. If we took the same metric and applied that to 4x5 films, using our 60 lp/mm figure, then we need a scan of near 330 MP to capture all that information. This is were the claims of 200 MP to 400 MP originate. A P65+ cannot hit 80 lp/mm in any test, despite that the files sizes suggest that. So is it really a 60 MP capture device? In fact, is the Nikon D3X really a 24.5 MP camera, or the Canon 1Ds Mark III really a 21.1 MP camera? When you look at what is really captured, then the file sizes are roughly 40% or more larger than the actual capture capability.

You choose not to comment on my reverse suggestion, that only 36 lp/mm on 4x5 film is needed to match the theoretical capability of the P65+. That is a number that is easily in reach of most 4x5 lenses, and at f22 in many situations, even using most ISO 100 colour films. If we considered the actual resolving capability of a P65+ MFDB, assuming it can reach 60 lp/mm, then we only need about 27 lp/mm on our 4x5 film. Those numbers are ridiculously easy to obtain for nearly anyone shooting 4x5 film, and within reach of many scanners. So how can you claim that a 39 MP back is almost better than 4x5 film, and a 60 MP back is better, when the results just don't hold up to your math?

http://www.hevanet.com/cperez/results.html

http://www.hevanet.com/cperez/testing.html

I stand by my statement that the top MFDB does not equal the capability of 4x5 film in one shot. I will not claim that 4x5 film equals 300 MP of data, and I have neveer stated that, though I do state that often the file sizes can approach that large size in order to capture all details on the film (this is backed up by a few others operating various high end drum scanners). I have handled many files from high end MFDBs and many scanned 4x5s, and I have yet to see any MFDB match the capability of modern 4x5 film. Many times 4x5 film and MFDB usage is beyond the needs of the final printed image, but it is nice to have that cropping reserve when you want it.

Ciao!

Gordon Moat Photography (http://www.gordonmoat.com)

bglick

18-Jan-2009, 19:21

> First off, there is no tremendous upres potential that a digital sensor has over scanned film, and if you think there is then you don't know what the hell you are doing.

I am sure you understand, you are in the minority on your position here... if there is no benefit, then why sharpen at all? Regardless, I have left this out of the equation. My 15 years experience has demonstrated otherwise, we can agree to disagree. But, I won't accuse you, of, not knowing what the hell you are doing. If both of us become un civil they will shut down the thread.

> Upscaling, no matter what software magic you throw at it, never increases resolution, it only increases file sizes.

We can start to get into semantics here....but I agree it won't increase the recorded resolution, but it will increase the perceived resolution of the final product, which is what most photographers are after. Anyway, i addressed this in my last post, so no reason repeating it, we can respectfully agree to disagree...

> It seems too much that you are pulling numbers to suite your own conclusions,

The Fuji numbers are all from the Fuji data and discussions with Fuji film engineers.... so where is the falsehood in these MTF values for color film? I will have to re check Perez's site, IIRC, at the contrast ratio of the targets, 120 lp/mm was used... as you know, there is some very high resolving B&W films.... such as Gigabyte. (can't even recall if that is the correct name - I have not used it in years)

> Your choices of using math is falling far short of convincing me of anything,

Gordon, in all due respect, its not my job to convince of anything. I offered the information, which you have not found one serious objection to.... (you argue results, but never my process) yet, you claim you are not convinced ? Maybe you don't understand it, maybe you refuse to understand it, its not my job to figure it out.... remember, I am not getting paid for this.... you seem to think it's my job to convince you?

> so once again if you think any modern MFDB or DSLR equals 4x5 film, then re-photograph the 4x5 and prove it. The test is so simple.

The objective when doing comparative testing, is to remove as many variables as possible. I have done this. Your proposed method is to introduce added variables to the test (re-imaging the film with a digital camera??) . This added variable will can only degrade the test, not improve it. You are adding an 2nd generation for no good reason, sorry, this makes zero sense. If this method suits your style, then so be it...

> Do I think a circa 24 MP capture equals 4x5 Fuji Astia 100F or Velvia 50? No,

I can only assume you are mis-reading, or not understanding what I have written....can you please show me where I made this claim??????

> I suggest you actually try to replicate what your math suggests, and then try to figure out why it simply doesn't work that way.

Again, you are not reading, or not grasping what I am writing, please re-read.... we are in agreement on this, (24MP can not match 4x5) not sure why you are picking a fight here?

> If we took the same metric and applied that to 4x5 films, using our 60 lp/mm figure, then we need a scan of near 330 MP to capture all that information.

OK, we seem to be on the same page on the P65+... which btw was the result of 1/R, the same formula you are disputing, or not understanding, or dismissed, or whatever.... Now, on the LF film... lets assume you have recorded 60 lp/mm to LF film (I never suggested this was impossible)....but now we seemed to be disagreeing with simple math... as you suggest, using the same metric to convert to MP's of recorded resolution...

60 lp/mm = 120 pixels per mm

90 x 120 = 10,800

120 x 120 = 14,400

10800 * 14400 = 156 MP

Please explain where my math has gone astray? how do you get 330 MP??? I am asking for your help Gordon. And please don't respond by saying the scanned file is bigger, because - it's YOU who emphatically states, you can not add resolution after it's captured. So you provide the resolution on film at 60 lp/mm, and yet we still disagree on how many MP's this equates to? by a factor of 2x? I remain open to your ideas....

BTW, this scenario would require film at 120 lp/mm MTF and a diffraction limited f11 large format lens.... clearly on the edge of "what's possible", but thats irrelevant, lets try to agree on the elementary math first...

> You choose not to comment on my reverse suggestion, that only 36 lp/mm on 4x5 film is needed to match the theoretical capability of the P65+

36 lp/mm on 4x5 = 56MP... as my previous posts demonstrate, this is more than P65 can resolve. So why do you keep suggesting I choose not to comment on this....its all above? Are getting the complete thread?

We have two different approaches Gordon.... you start at, lets get down to nitty gritty, but then, you don't know WTF 1/R (a basic imaging premise), nor do you want to learn or embrace it....then you start tossing out scenarios where none of the details nailed down, which is how this entire comparative issue has become a forum nightmare for years. My position all along has been, the DEVIL IS IN THE DETAILS.... and therefore the details must be nailed down for every comparison! Only then, the numbers make sense and match real world testing.

> So how can you claim that a 39 MP back is almost better than 4x5 film, and a 60 MP back is better, when the results just don't hold up to your math?

The results will hold up, if you input the right variables. Its the old adage, garbage in, garbage out...... but unless the details are pinned down, the claims can go in either direction....your generic scenarios like this above, IS the source of all the confusion. State, lens, f stop, MTF of film, and the same with the MF back... then you can make a sensible comparison of the two....

> I stand by my statement that the top MFDB does not equal the capability of 4x5 film in one shot.

Consider this..... ISO 800 speed color neg 4x5 film with vintage 1880 era lenses, vs. 60 MP digital back with digitars. Do you still take the same position? Is it starting to become clear, you can't generalize like this ? Its all about specifics Gordon!!!

Ciao!

bglick

19-Jan-2009, 08:25

BTW, dh, the link you provided, which I finally glanced through it...

motamedi.info/speed.htm

very impressive findings.... this demonstrates with a little research and testing, you can still find some vintage gem lenses for a small fraction of $ new LF lenses. Of course, considering QC and tolerancing back then were nothing like today, the chances of variances between samples is great....so it would pay to start testing. Even today we see occasional examples of poor tolerancing which slips through QC. The last big case I recall was the Super Symar XL 80's, maybe 5 years ago, which IIRC, Schneider corrected.

The other final caveat in the resolution chain....which i did not have time to write in the last post.... is printing. Since this thread became a "resolution chain" mini-series, I feel compelled to mention it. I only tested ink jets, not the darkroom printers.

As discussed with scanners..... a good scanner can extract all the data from film....the better the scanner, the more efficient, therefore the smaller the file. However, always remember, it's the recorded MP's that exist in the file, NOT the file size backtracked by scanned pixels. So if you want 5 lp/mm to print, and you had to over scan by 2x to extract all the data from the film, you must send 2x the dpi to the printer to hold your 5 lp/mm. However, this assumes the ink jet printer / paper is 100% efficient... unfortunately, they are not...

About 5 years ago, I read some tests on this on the web.....then ran some tests for myself. I created perfect targets in Photoshop....then sent them to the printer at all different feed resolutions. I examined the finished print with a loupe. The results were all over the map based on paper type, printer type and rez feed rates. The results acted very similar to MTF on the imagining end. A lower resolution requirement on the print (1 lp/mm) made the printer more efficient. The higher requirement on the print, the less efficient the printer / papers became....sometimes up to 50% efficiency. So there are losses here as well...but its easy to test.

Fine art papers with inferior coatings are the worst of all the papers I tested. Hanamule Photo Rag being the best of the fine art papers I tested, and became my paper of choice for color LF prints. However, there is hundreds of papers to choose from and they continue to change coatings and manufacturing protocols. So testing is imperative... be sure to use the same printer drivers or RIPS when testing, as their is often additional interpolation going after the printer / RIP software consumes the file you send it.

sanking

19-Jan-2009, 09:30

First, I am not sure why you introduce the issue of ink jet efficiency into this discussion. That would apply equally to printing with both digital capture and film scans, would it not?

Then, can you point me to one specfic test that shows that one has to over sample by 2X to extract all the data from film? Since you place a lot of emphasis on the devil being in the details, I would be interested in these details. And no theorems please, just a good objective test that proves what you assert.

Sandy King

As discussed with scanners..... a good scanner can extract all the data from film....the better the scanner, the more efficient, therefore the smaller the file. However, always remember, it's the recorded MP's that exist in the file, NOT the file size backtracked by scanned pixels. So if you want 5 lp/mm to print, and you had to over scan by 2x to extract all the data from the film, you must send 2x the dpi to the printer to hold your 5 lp/mm. However, this assumes the ink jet printer / paper is 100% efficient... unfortunately, they are not...

bglick

19-Jan-2009, 09:34

Gordon, sorry I did not respond to your previous post yesterday...... today, I did a quick check on B&W film resolutions after reading your comment of...

> So I don't quite get how you are claiming that B/W film is so much better than colour film.

a few interesting bits...

From: http://www.camerahobby.com/Vignettes_BW.htm

Resolution – B&W film are still the highest resolution media available in photography with Kodak TMAX 100 the best of the lot among widely available films. There may be some specialty ISO 25 speed films that will outperform TMAX 100, but the days of ISO 25 films being used regularly have long disappeared and sadly one film that I had a penchant for in the past Agfa APX 25 has recently been discontinued.

Carl Zeiss recently published an article in their newsletter about film resolution and the results of their tests? Agfaortho 25 came out on top with the highest resolution with 250 lp/mm resolved and Agfa APX 25 came in at 200 lp/mm. The best color film was Kodak Ektar 25 (Royal Gold 25 at one time) also at 200 lp/mm, but this film is no longer available. The best currently available color film was Fuji Velvia, which was a fair ways back at around 160 lp/mm with Kodak TMAX 100 edging it out with 180 lp/mm. The next best color films came in at 150 lp/mm.

<snip> Of course, we must adjust for target contrast, and preferably have some MTF data to work with... but regardless, there is a LOT of high resolving B&W films. So I disagree with your position that B&W films not the highest resolving films....well suited for target testing.

> It seems too much that you are pulling numbers to suite your own conclusions, and I am not seeing these backed up in reality.

Lets start out with the links you provided. The Tmax 100 pdf file, on page 8...if you view the MTF curves, at the spatial frequency of the targets we would use, I would suggest that 120 lp/mm is a reasonable number to use in the 1/R equation.... your links supports this well.... thank you for providing them.

Next, you suggested that Fuji Astia 100 out performs Tmax 400....???

Looking at the MTF charts in the pdf files you linked, 50 lp/mm spatial frequency, (typical rez of a target we would use)

Astia 100 delivers 35% contrast....

TMax 400 delivers 70% contrast (2x that of Astia)

Tmax 100 delivers 100% contrast (3x that of Astia)
(this is why Tmax 100 is such an ideal film for target testing)

So now I am really confused....what is the basis of your allegation that these numbers are pulled out of mid air? You provided these links, did you actually read the MTF charts ? Again, I am not following your logic here either...please do explain what I am missing....

> You make assumptions and then plug your assumed numbers in order to inflate your weak arguments.

So far Gordon, you have provided ZERO information which refutes any of the numbers I have provided. In addition, the numbers and formulas I provide don't come from me, these are just regurgitated formulas and MTF values that have been used by Fuji, Kodak, Zeiss, Leica, Schneider, etc. since the early 70's. The film data comes direct from the manufacturers data. And when you run the tests, interestingly enough, the results are quite predictable and support the equation and the MTF values of the film / lenses. It works when Zeiss runs their tests, it works when I run my tests, it works when Perez runs his tests, and thousands of others. I am surprised you take such a hard line position, when you have admittedly never performed these resolution tests, and clearly write, "WTF is 1/R"... ?

> Your choices of using math is falling far short of convincing me of anything,

You may want to take your case to the major manufacturers of lenses and film. Explain to them how their million$ in research have all been wasted, and the MTF concept as well as the equations they have used and proven through the past 50 years are all bogus. If you do, please to report back to us.

For many of us simpletons, we read the information, we comprehend it, then test it.... THEN we draw our conclusions if the numbers make sense. In all my experience testing, the numbers always make sense. Are they +/- 3%, no, not that accurate, as there is some subjectivity reading targets. But as mentioned, the purpose here is to get "close", and in this case, debunk outrageous claims that are often being tossed around here, where errors can be in the 10x range. (400 MP for scanned 4x5 film?) If this testing methodology was as bogus as you suggest, or as inaccurate, do you think it would have been promoted for so many years? Other pros and optical engineers would have not found the flaws by now ???

> You make assumptions and then plug your assumed numbers in order to inflate your weak arguments.

My Arguments? All the data I use comes from manufacturers and proven imaging fundamentals. Can you be more specific.....just what am I inflating? As always Gordon, I remain open to your comments.

> If you believe so highly in your theories and number choices, then back up your claims,

Once again Gordon, none of these are my theories, or my MTF data. I don't know what else to provide you ... it might be helpful if you read-up on the subject. I would still suggest, if you disagree with all these wild assessments, please provide detailed information on where everything has gone astray..... Fair enough?

bglick

19-Jan-2009, 09:52

> First, I am not sure why you introduce the issue of ink jet efficiency into this discussion.

Because this discussion moved to "the print" and working backwards from the print to determine enlargement potential, so it made sense to introduce it? Would you prefer i pull the post?

> That would apply equally to printing with both digital capture and film scans, would it not?

correct....

> Then, can you point me to one specfic test that shows that one has to over sample by 2X to extract all the data from film? Since you place a lot of emphasis on the devil being in the details, I would be interested in these details.

Sandy you will have to do your own research on this.... really, not only have I spent hours posting all this, now I am supposed to be the R&D support system for everyone who wants supporting information for any information they are not sure of ?? I guess thats the thanks ya get on internet forums... sheeeeesh

For starters, is there any re-imaging method that is 100% efficient? Obviously no. I used the number 2x as an example.... the range of scanners people use are everything from desktop scanners for $99 to $80k drums scanners.

As I mentioned previously, scanning is a form of imaging, a subject plane, an optic and an image plane. It is subjected to the same fundamentals as any other form of imaging. Yes, it does have the benefits of software manipulation before the final file is produced....and that is unique to each scanner. But the same imaging principles apply.

Place a 100 lp/mm target on your high end scanner and scan at that same resolution, see if you can resolve it....if it fails to resolve, see how much higher you must scan to resolve it... that will advise you of your scanner eff. at that spatial frequency. You will find at low spatial frequencies, scanners are very eff....at higher frequencies, they become less eff....., just like the MTF of lenses and film in the photographic world....

Many scanners automatically oversample by default, then downsize when they deliver the file....and I don't have a R&D dept. to bring all the scanners in, and test these details..... so again, there is many variables..... but the good news is, you can run your own test, with your own scanner, and then you can make a contribution to this thread by reporting your findings... OK?

All my scanners have been very eff.....mainly drums, and Cezanne Elite... your mileage may vary...

dh003i

19-Jan-2009, 11:00

Sandy you will have to do your own research on this.... really, not only have I spent hours posting all this, now I am supposed to be the R&D support system for everyone who wants supporting information for any information they are not sure of ?? I guess thats the thanks ya get on internet forums... sheeeeesh

Don't ya know you're a slave? ;-)

Sincerely, I thank you for the help you've provided me, in understanding lens resolution.

bglick

19-Jan-2009, 11:26

> Don't ya know you're a slave? ;-)

yeah, actually I do know this stuff, which is why I disappear off forums for years at a time... it's a thankless job :-)

> Sincerely, I thank you for the help you've provided me, in understanding lens resolution.

Thanks for the kind words.... If the thread helped one person, then it was worth it :-)

sanking

19-Jan-2009, 16:40

"andy you will have to do your own research on this.... really, not only have I spent hours posting all this, now I am supposed to be the R&D support system for everyone who wants supporting information for any information they are not sure of ?? I guess thats the thanks ya get on internet forums... sheeeeesh"

I have done my own research, and a lot of testing scanning resoution targets as well. My experience is absolutely not supported by your claim that it necessary to over sample at 10 lines per mm to get 5 lines per mmm on the print. It may be that your claim is supported by some previous testing, which is why I asked if you could point me to a study. What do your studies, assuming you must have made some, show?

You are the one who is claiming the devil is in the details. I simply am asking for some details to support a claim that you made.

Sandy King

sanking

19-Jan-2009, 16:52

[QUOTE=bglick;431718
Place a 100 lp/mm target on your high end scanner and scan at that same resolution, see if you can resolve it....if it fails to resolve, see how much higher you must scan to resolve it... that will advise you of your scanner eff. at that spatial frequency. You will find at low spatial frequencies, scanners are very eff....at higher frequencies, they become less eff....., just like the MTF of lenses and film in the photographic world....

[/QUOTE]

Not many people have a high end scanner that can resolve 100 line pairs per mm so that test is off limits for me.

What I prefer to do is look at the resolution target on film with a microscope. Generally 30X-40X is high enough magnification, but you might need more for some fine grain B&W films. You can immediately tell from this exercise how much resolution the film is resolving with the camera system and development used.

Now scan the target and see how how you will have to set the resolution to caprture what you can see with the microscope. In work I generally over sample a bit, but I don´t find it necessary to oversample by 2X, not even close.

Sandy King

bglick

19-Jan-2009, 17:26

> I have done my own research, and a lot of testing scanning resoution targets as well. My experience is absolutely not supported by your claim that it necessary to over sample at 10 lines per mm to get 5 lines per mmm on the print.

Sandy, please re-read what I wrote. I did not suggest that all scanners need to over-sample by a factor of 2x to extract film data. I made it CRYSTAL clear, the better the scanner, the more efficient. The lower the spatial frequency of the target, the greater the efficiency of the scanner.

In your case, you have a very high end scanner, I did not suggest it would require 2x oversampling.... so I don't dispute your findings at all, they agree with my findings with all my scanners through the years.... As I made it clear, I used 2x as an example in the "printing" post, for simplicity sake. Then I suggested everyone test their own scanner to determine the efficiency....your testing is with your HIGH-END scanner.....but what about a $99 film scanner, will it perform as well as yours? Get it? I was simply laying out the protocol so others could get a feel how there scanners measure up....that post was not addressed to you specifically....IT WAS GENERIC!

In my case.... with low spatial frequencies, I can scan within 10% of the film rez. AT very high frequency on the film, say 60 lp/mm, I scan at about 1.3 - 1.4x the film rez. As I mentioned previously, every scanner will vary based on the hidden firmware that dictates the scan process and the specific characteristics of scanners optical chain.

> You are the one who is claiming the devil is in the details.

yes, the devil IS in the details, and I am suggesting to determine your specific "details", TEST YOUR OWN SCANNER ! I never suggested that I possess ALL THE DETAILS OF EVERY SCANNER EVER BUILT ON THE PLANET ?? You gotta be fair, so this clearly deserve a double sheeeesh...

sheeeesh.....sheeesh....

> Now scan the target and see how how you will have to set the resolution to capture what you can see with the microscope.

Sandy, do you realize, your testing procedure above is repeating the protocol I wrote from the beginning? So whats the beef? It's that simple, - test IT! If you go back in this thread, I suggested a range of over sampling that may vary from 1.2x - 3x based on the quality of the scanner and the frequency of the target... I am sure a $99 scanner even at 3x over sampling will not extract high frequency targets.... hence the HUGE range I tossed out as an example, due to the WIDE range scanner quality at all many different price points...

Are we on the same page yet?

I feel like I am in a Twilight Zone episode...

Gordon Moat

19-Jan-2009, 18:22

bgclick, or whatever your real name is, I refer back to the origination, and some individuals comments:

http://www.largeformatphotography.info/forum/showpost.php?p=429612&postcount=3

http://www.largeformatphotography.info/forum/showpost.php?p=429772&postcount=5

http://www.largeformatphotography.info/forum/showpost.php?p=430385&postcount=26

I am left curious as to your background, though I suspect engineer; which might explain the fascination with numbers. Your quoting method is so different from that of anyone else who posts on LF Forum, that it has become tedious to respond to you.

I suggest you research people like Sandy King prior to suggesting their methods are improper, or that they lack thoroughness. While I rarely agree with Lenny Eiger, I am finding similar results to his in real world images, namely that your numbers just don't match the image results out there; basically what you introduced into this thread about the issue of Image Quality.

http://en.wikipedia.org/wiki/Digital_versus_film_photography

I suggest you tackle this Wikipedia article, because your efforts will be better spent addressing the citations needed areas. Likely you will find a larger audience.

http://www.galerie-photo.com/film-contre-silicium-resolution.html

I don't know if you read French, but I greatly respect the views of Emmanuel Bigler. Galerie Photo is also a very informative and extensive website, which I highly recommend.

Finally, if I were to accept your figures at face value, they are at odds with the reality of actually seeing highly detailed prints from Gursky, Burtynsky, et al. Perhaps these photographers have beaten the math.

Ciao!

Gordon Moat Photography (http://www.gordonmoat.com)

bglick

19-Jan-2009, 20:23

> I am left curious as to your background, though I suspect engineer;

Guilty as charged... but I have been involved in photography and optics for over 30 years. Not just camera optics...

> Your quoting method is so different from that of anyone else who posts on LF Forum, that it has become tedious to respond to you.

This explains why we are struggling so much with the MTF stuff :-) if you see ">", that's a quote from you.... everything else is fresh, from me... OK? No one else seems to struggle with this...

> I suggest you research people like Sandy King prior to suggesting their methods are improper, or that they lack thoroughness.

I am back in the Twilight Zone episode.... are you reading what I WRITE? I did not suggest ANYTHING was improper with Sandy's protocol, his suggestion repeated EXACTLY what I had written previously, hence the confusion I had. I get the feeling no one is reading what is written in these posts...which is a huge source of frustration....

the Wikipedia link is a very basic primer on digital vs. film... not much to disagree with... other than, in our examples here, we are leveling the playing field between all the formats, by stating "recorded resolution in MP's" vs. native MP's. We have done this for both film and digital....this accounts for 1/R AND the recording media size...the two factors that dictate total resolution. It's my suspicion, you have gazed over this part.... this effects the numbers greatly... I could be wrong, just trying to find the parts you disagree with as NEVER mention specific faults...

I don't read French...sorry...

> Finally, if I were to accept your figures at face value, they are at odds with the reality of actually seeing highly detailed prints from Gursky, Burtynsky, et al. Perhaps these photographers have beaten the math.

If Gursky and Burtynsky have overcome the laws physics, the laws of imaging, they should be nominated for a Nobel Prize. Really.... no joke there. I can assure you, if they have defied the basic laws of imaging, Zeiss, Leica, Schneider would offer them million$ for their discoveries. :-)

Gordon, as I am sure you would agree, our communications is failing, and my fingers are tired of typing. I explained everything in great detail.... I have given you ample opportunity to suggest where the faults are....and yet, you have not offered one bit of information that is conflict with basic imaging laws. IMO, you have added fuel to the fire of, THATS NOT WHAT I SEE, and FILM RECORDS 400 MP, all with no details...etc. The problem, as I pointed out many times, is without details of "what you see", your position can not be evaluated. This is the value of "seeing" and testing with targets.

I am sure you see great prints, but there is a lot that went into that great print, and without all the details, its meaningless to introduce such into these discussions. The testing procedures are simple, you are welcome to try them any time, it costs just a few dollars.... so why not put the rubber to the road and get to the bottom of this? Again, your conclusion is, yourself and Lenny have proven Kodak, Fuji, Leica, Zeiss wrong, by a factor ~10x.... (under normal or avg. photog scenarios) of course, no justification, no tests, it's all based on what you see in certain images... too many variables to make constructive comparisons.

To close this issue out, as this is getting way too repetitive.... I would leave you with two statements that demonstrate how the range of details (which are usually left out of the discussion) can span the gamut, which is why this issue is all over the map..... These are two extremes Statements, which both "can" be true.... I won't repeat the details of the math, as its all in this thread...

Film vs. Digital capture

STATEMENT #1 - "FILM CAN RESOLVE 74x GREATER THAN DIGITAL"

(I purposely leave out details, cause therein lies the problem)

Film capture details...
8x10 B&W film 100 lp/mm MTF, diffraction limited f11 lens, highly detailed subject, infinity focus, tight camera, excellent processing, etc.
This scenario we will record 666 MP of resolution. (this is feasible)

Digital capture details
24 MP DSLR with slightly aberated lenses delivering f11 aerial rez...
This scenario will record 9 MP of resolution.

666 / 9 = 74x yep, it checks out, this Statement can easily be justified... the luster of LF film is still alive n well !

STATEMENT #2 - MF DIGITAL CAN RECORD 7X MORE RESOLUTION THAN MF FILM.

Film Capture details
MF 6x4.5, ISO 400 color neg film 40 lp/mm MTF, shot at f16 for DOF...
This scenario will record 8 MP of resolution

Digital Capture Details
P65+ back, Digitar lenses at f4 (diffraction limited), shot at infinity...
This scenario will record 42 MP of resolution.

42 / 8 = ~ 7x Yep, this checks out too, statement can be justified.

Get the drift here? This is why this debate is so insane... the answers run the gamut, from the first Statement where film BLOWS away digital by 74x .... and the second statement where MF digital blows away MF film. How can both be true? It all comes down to the DETAILS of each captures variables......, f stop used, DOF, subject detail, film type, format size, focus distance, ... etc. etc. etc. If I introduced view distance in the equation, I could really swing the numbers even further apart. AS you can see, the details can swing the outcome in either direction. And this happens in the real world, you get people comparing images without the details, and they come to incorrect conclusions.

This is why, when I hear statements like, "thats NOT what I see" .... I have to ask... what distance were you viewing from, what printing method was used, what capture method, what film or sensor, what lenses, what f stops, how much DOF, etc... only then can we make sense from "what I see" comments. Then of course, you need a sensible comparison to do a comparative analysis. For the newb, yep, this can be tricky stuff, lots of variables. But at least one photog on this forum digested this entire thread in just a few hours.... and has his Excel spreadsheet cocked and loaded :-)

Gordon, you call this "being obsessed with math." I respectfully disagree. In my world, I would classify this as "implementing 6th grade math to pre determine the outcome of my imagining." It's a simple and powerful tool to plan a shoot. I can determine what format too shoot, what lenses, how to scan, how to print, what paper, what view distance, etc. etc. It takes me 10 minutes to run a scenario, thanks to spreadsheets...its no big deal... It's basic imaging fundamentals reduced to a handful of variables.... quite elementary stuff......and the best part is... its proven!

Now, you should be happy, I justified your position, film records 74x more than digital! :-) yeee ha!

dh003i

19-Jan-2009, 20:55

Film capture details...
8x10 B&W film 100 lp/mm MTF, diffraction limited f11 lens, highly detailed subject, infinity focus, tight camera, excellent processing, etc. This scenario we will record 666 MP of resolution. (this is feasible)

First, do you mean 100 line pairs per mm, or 100 lines per mm? I know that your nomenclature was for line pairs per mm, but 100 lp/mm seems really high.

And even 100 l/mm seems high for a lens covering the entirety of an 8x10 lens at f/11. The Nikkor-SW 90/8 (and presumably 90/4.5 as well) has a measured resolution to BW film of 80 across the board at f/11. That's (80 x 25.4)^2 x 8 x 10 / 10^6 = 330 megapixels. But I'm not sure if Chris Perez measured it far enough out where it would need to go to cover 8x10 (it does cover 8x10). Does "edge" resolution mean edge of the film without any shift, or the lens shifted such that you're measuring the resolution from the very edge?

dh003i

19-Jan-2009, 21:19

Regarding the over-sampling a scanner needs to capture all of the resolution of film, doesn't the 1/R formula imply that a scanner can never capture all of the resolution of film?

I.e., a 6000 dpi scanner corresponds to 6000/26.4 = 236 l/mm. Assuming an image recorded to film at 80 l/mm, the final resolution on your computer would be:

R = 1 / (1/236.22 + 1/80) = 59.76 l/mm

and that's over-sampling by almost 3 times. Granted, it is very very close...but without over-sampling (as some people would think you can do), you would get

R = 1 / (1/80 + 1/80) = 1 / (1/40) = 40!

So without any over-sampling, your final resolution is cut in half!

Take a look at these numbers (calculated the same way as above); it really sucks:

Over-sampling ; Actual Resolution (of scan)
1.0 x ; 20.6 Mp
1.1 x ; 22.7 Mp
1.2 x ; 24.6 Mp
1.4 x ; 28.1 Mp
1.8 x ; 34.1 Mp
2.6 x ; 43.1 Mp
4.2 x ; 53.9 Mp
7.4 x ; 64.1 Mp
13.8 x ; 71.8 Mp
26.6 x ; 76.7 Mp
52.2 x ; 79.5 Mp

But the resolution of the film itself is (80 x 25.4)^2 x 4 x 5 / 10^6 = 83 Mp.

dwhistance

20-Jan-2009, 02:52

I have followed this thread with interest as I have the previous similar threads, albeit that it is clear that the participants are tiring of it from recent posts.

I agree with, and understand, the math used by bglick and wholeheartedly agree that "THE DEVIL IS IN THE DETAILS", however I think this is exactly where many of these discussions go wrong. This is because there is a tendency, at least in the mind of the reader, to compare say the MF digital back used with a lens at optimal aperature with 4x5 film with the lens well stopped down. ie apples with oranges. This is similar to the medium format example given above although I realise that bglick used it to make just this point.

I also feel that not enough thought has been given to the nature of the pixels in the digital back, particularly in one shot mode, where even the P65 doesn't really have the stated number of "real" pixels but a greatly reduced number due to the Bayer pattern. Quite how many I am at a loss to say but the reduction must be significant given that you essentially need a block of 4 pixels to generate accurate colour. Simplistically that would suggest a reduction of perhaps 50% to 75% although it would be good to know what it really is. I know this will raise all sorts of comments on the wonderful algorithms used in the processing, however that doesn't change the fact that interpolated data, however well it is done, is not the same as real data - we are essentially back to the point bglick made, correctly, about scanning.

Perhaps the impact of the Bayer pattern will go some way to explain the empirical findings of Gordon Moat, which I agree with, that in real life (landscape) prints 4x5 film appears to better MF digital backs by a wider margin than the calculations would seem to suggest. It would also explain why, when used in the studio in multi-shot mode these same backs can hold their own against larger film and even some scanning backs.

David Whistance

sanking

20-Jan-2009, 09:26

I agree that the quality of a pixel as it relates to film resolution is something of a black hole. The only way I know to compare the two is with specific testing of resolution targets, taking into consideration the angle of view of the lens and the size of the film versus the size of the sensor. You can get the results of resolution with digital capture directly, just by looking at the image on your monitor at high magnification and doing the number. Film is much more complicated because it is dependent on both the film (color or B&w, grain, ASA) and the quality of the scanner.

As others have said, there is no one magical answer to this. It really depends on the details.

Sandy King

I

I also feel that not enough thought has been given to the nature of the pixels in the digital back, particularly in one shot mode, where even the P65 doesn't really have the stated number of "real" pixels but a greatly reduced number due to the Bayer pattern. Quite how many I am at a loss to say but the reduction must be significant given that you essentially need a block of 4 pixels to generate accurate colour. Simplistically that would suggest a reduction of perhaps 50% to 75% although it would be good to know what it really is. I know this will raise all sorts of comments on the wonderful algorithms used in the processing, however that doesn't change the fact that interpolated data, however well it is done, is not the same as real data - we are essentially back to the point bglick made, correctly, about scanning.

David Whistance

bglick

20-Jan-2009, 09:33

.

> First, do you mean 100 line pairs per mm, or 100 lines per mm? I know that your nomenclature was for line pairs per mm, but 100 lp/mm seems really high.

lp/mm = Line Pairs Per mm. You are confusing the MTF of the film, vs. the recorded OFR. (On Film Resolution) Remember?

> And even 100 l/mm seems high for a lens covering the entirety of an 8x10 lens at f/11. The Nikkor-SW 90/8 (and presumably 90/4.5 as well) has a measured resolution to BW film of 80 across the board at f/11.

The same 1/R math applies ....

1/(1/(1500/11) + 1/100) = 58 lp/mm recorded to film
(not 100 lp/mm)

58 x 2 = 155 lines per mm

200 * 250mm for 8x10 film = 666 MP

> Does "edge" resolution mean edge of the film without any shift, or the lens shifted such that you're measuring the resolution from the very edge?

Edge rez, equals the resolution recorded at the edge of the film, in this case, usually the 8" edge, or 4" radius from center. I only used this f11 lens as BEST CASE scenario for the 810 film.... I am sure there is a dandy f11 lens optimized for infinity focus, as you have already found some vintage lenses that perform near diffraction limits for a specific focus distance and a given f stop....

Your scanning comments are valid, however, there is tooo many variables to reduce this to math, as you are forced to make too many assumptions. Hence my suggestion for simple tests to determine the answers you are pursuing... a few generic comments:

1) You never know how much over scanning is being performed by the scanner, as it's common for scanners to over-sample and reduce file size without your knowledge.

2) Using 1/R for scanners, you must treat it the same as our camera imaging system, you must enter BOTH the MTF of the lens (just like a camera imaging system) and the MTF of the targets. Just as a side note....why do expensive scanners perform so well? A diffraction limited f4 - f5.6 macro lens such as a digitar, cost $2k+ just for the lens, not to mention all the mechanicals, lighting, electronics, software, etc. So for lower end scanners, with lower end lenses, often times high frequency targets can NEVER be resolved, regardless of the dpi advertised on the box....its just native pixel count, which is only one component of 1/R. This is why the entire issue, unlike camera imaging, is a pandoras box.... there is too many variables we do NOT know, hence the simple scanner test both I and Sandy proposed, will determine the capability and efficiency of a specific scanner.... in effort to prevent this thread from turning into a scanner thread, I will stop there...

> Quite how many I am at a loss to say but the reduction must be significant given that you essentially need a block of 4 pixels to generate accurate colour. Simplistically that would suggest a reduction of perhaps 50% to 75% although it would be good to know what it really is.

1/R math is basic imaging math.... it is pre dates digital capture. However, digital sensors have their own MTF, although we are not provided specific MTF data, the pixel density and sensor sizes are clearly defined. Your point regarding Bayer RGGB pixel layout is valid. Bayer sensors introduce this added variable of color pixel sites.

Without getting too involved into digital recording..... here is the reality of the RGGB pixel layout as it relates to 1/R.....this is from my own experience shooting color targets. There is 3 general classifications....

1) When shooting black targets, 1/R prevails, remarkably accurate. Because all pixel sites will "see" the B&W targets.

2) When shooting Green targets, 1/R outcome is "nearly" identical to B&W targets.

3) When shooting R, B targets, there is clearly a fall off, in the 25% range.

In addition to color variable, the fixed grid pattern of digital sensors, does not record mis aligned targets as efficiently as those targets on the same XY grid orientation. At high enough frequencies (dependent on sensor density) 45 deg angled targets create new degradation issues with digital capture (vs film). Target orientations that align with the XY sensor pattern perform as expected, no losses. However, targets at 45 degrees to the sensor grid, DOES introduces added degradation, BUT again, only above certain frequencies. So, based on the subjects you shoot, this "can" be a very unwelcomed shortcoming.

And yes, flat bed scanners are vulnerable to this same orientation issue, hence the need to over sample. Drum scanners are almost immune to this issue, due to their non XY recording.

When I first start testing digital cameras, I expected huge losses due to these potential shortcomings....but in reality, they are very minor.... the reasoning is two fold.... first, many colors are a mix of several colors, which allows the pixels to acknowledge the existence of colors which are not a perfect match to the pixel recording color. Secondly, the brilliance of the interpolation algorithms in the camera are nothing short of amazing. Other than pure RED, or pure BLUE targets (specially at 45 deg. orientation) the Bayer sensor technology performs almost as well as a Foveon sensor where each pixel site records RGB. Its VERY easy to test this with color targets, placed at different orientations throughout the recording area. I made a long post about this in more detail, in another thread awhile ago - if anyone is interested....but that's the short story.

> I know this will raise all sorts of comments on the wonderful algorithms used in the processing, however that doesn't change the fact that interpolated data, however well it is done, is not the same as real data

If you ever tested this, you would be shocked at how effective the entire working system is. Because all these pixels "see" small components of other colors, the software really does an excellent job interpolating....BUT, its not a 100% guess as some suspect, as it does have "some" data to work with.....so the "PURE" interpolation is limited to distinct color subjects, mainly R or B. Which if a subject is 100% of one these colors, it would reduce the "effective" native pixel count by 75%. In which case, the resultant recorded resolution does take a serious hit.

> which I agree with, that in real life (landscape) prints 4x5 film appears to better MF digital backs by a wider margin than the calculations would seem to suggest.

I shoot a lot of 4x5 Velvia at f16 with my SS XL 110 and 150... Excellent 4x5 lenses. The DOF fits within these shots, as I pick n choose shots carefully. This will record ~ 70 MP of usable data (MTF of the film at 70 lp/mm) Compare this with P65+ with adjusted f stop for format size, it will record 31MP (at best due to color and orientation issues). With the previous 39MP backs, even less, just guessing, in the 24MP range.

So it's NO mystery to me, why all my 60" prints from 4x5 Velvia exceed MFDB capture, including the newly introduced P65+ (which I have not tested, but the math will surely predict its gains). So IMO, there is no...

" wider margin than the calculations would seem to suggest"

I consider 3x the resolution to be very substantial. IMO, the calculations actually justify the higher resolution 4x5 output.

However, when you begin to stop down on 4x5, (or 810) the gap begins to narrow quickly.... it's a game - success lies in avoiding the fatal effects of apt. diffraction - the larger the format, the faster it reduces recorded resolution.

And you have correctly pointed out, when you begin to stitch a few digital captures together, it's a game-changer... hence why, there is a LOT to consider when making these comparisons. There is also a lot to consider, when selecting your capture weapons for your specific subject matter and output criteria.

bglick

20-Jan-2009, 17:42

One final "feather in the cap" for film !

I have long considered my Mamiya 7 camera system, one of the gems of color landscape photography (of course B&W as well). Granted, it does not have movements, but the lenses are beyond exceptional. The camera has film flatness second to none (critical for wider f stops)..... and a complete kit is quite a small package to carry. No film holders, loupes, hoods, etc. The 43mm WA lens is about the BEST WA lens ever built, in ANY format. Most all of the lenses up to the 80mm can be classified as diffraction limited, at least 30mm out on the image radius... Tilt is much less useful with fl's this short. Occasionally you miss front rise...

As an example, an f4 infinity shot with Velvia will record 67 MP of resolution. (56 x 69 mm format) At f5.6, 58MP. Compare this with the new P65+, adjusted for f stop, maybe 40 MP max. Stitch a few shots, and it too is a game changer...

Eat that Phase ONE! :-)

And the real beauty is... the 120/220 roll film can be scanned very effectively with the Nikon 9000 and Minolta MF scanners. Too bad they are no longer in production, but they can be had quite cheap on the used market... maybe there is some new Nikon 9000's still around? Anyway, a wonderful alternative to LF and Digital...

Sheldon N

20-Jan-2009, 20:37

Okay, this may be a sidebar to the discussion here, but I thought I'd throw out a question and double check on a fundamental assumption I had about film format size and ultimate resolution.

Much of the shooting I do ends up with me stopping down to get depth of field, movements or no movements. I'm not talking about crazy f/64 kind of stuff, but just your every day f/32 ish on 4x5.

When you start with the assumption that you need to stop down to get sufficient DOF for a shot, and that the result of stopping down to get sufficient DOF puts you in territory where you are diffraction limited - doesn't the scaling of formats inversely parallel the required aperture for DOF to the point where changing the format size doesn't change the system resolution?

By the time you stop any of these ultra high resolution cameras (25MP DSLR , MFDB, 6x7 film, 4x5) down to a working aperture does the choice of format size become offset by the required aperture to achieve suffient DOF (movements aside)? I always assumed we were working with either the choice of resolution vs DOF for much of the typical landscape work that I do.

I know the math doesn't hold up exactly true, but isn't it an approximate rule of thumb?

bglick

21-Jan-2009, 00:46

Some really nice shots Sheldon.... love the old building..

Since most of my responses create more hardship than benefit, it's best someone else tackles your DOF question...

jb7

21-Jan-2009, 05:35

Since most of my responses create more hardship than benefit, it's best someone else tackles your DOF question...

Well there you go again, falling into the trap of making unfounded assumptions, and ignoring the details-

I've found this thread fascinating, both the claims and the responses.
Although I suffer from an intellectual lassitude that prevents me from testing any of the formulae and calculations, in general, they do seem plausible-

However, the performance of an imaging system is not the only criterion by which a photograph might be judged;
although a 200mm ƒ/2 used at full bore on 35mm might produce the prettiest pixels, I myself would find very little use for it in photographing interiors.
Or pretty much anything else, for that matter.

I do have a 9" ƒ/2.5 projector lens which covers 8x10 at portrait distances, which would make some members here reach for the trashcan.
Its value (if it has any) might be in its rendition of background out of focus areas- where tonal transition might be more important than resolution-
because, actually, there isn't any-
Also, the fact that on a view camera I can place the plane of focus where I want it
rather than being forced to use it axially and perpendicular to the subject plane gives me much greater freedom in composing an image,
and I look forward to being able to make contact prints from large originals, when I eventually get my processing setup sorted out.

But I know this is off topic-

I think I have a better grasp of the capability of imaging systems as a result of this thread, and I'll definitely spend some time re-reading it, when I get a chance-
I can only speak for myself, but I do appreciate the rigour that has gone into the testing, and the presentation of the results-
and it will have a bearing on how I might make photographs in the future-

Just don't test me on the details-

joseph

sanking

21-Jan-2009, 08:52

Ditto your remarks about the Mamiya 7 system with its wonderful array of lenses. If you can live without shifts and tilts this system is easily capable of 4X5 image quality with a fine grain slow speed B&W or color film. As mentioned, tilt is not very useful with lenses of 43mm - 80mm, and most perspective problems can be resolved in Photoshop.

In testing fine grain films such as Tmax-100 and Fuji Acros I consistently get on film resolution of 70+ l/mm, and as high as 90+ with the 50mm and 65mm lenses.

I typically use the camera on a tripod, with apertures of f4 - f11 unless circumstances require greater depth of field. However, depth of fiield at f11 with the 43mm and 50mm lenses is already very great.

Sandy King

One final "feather in the cap" for film !

I have long considered my Mamiya 7 camera system, one of the gems of color landscape photography (of course B&W as well). Granted, it does not have movements, but the lenses are beyond exceptional. The camera has film flatness second to none (critical for wider f stops)..... and a complete kit is quite a small package to carry. No film holders, loupes, hoods, etc. The 43mm WA lens is about the BEST WA lens ever built, in ANY format. Most all of the lenses up to the 80mm can be classified as diffraction limited, at least 30mm out on the image radius... Tilt is much less useful with fl's this short. Occasionally you miss front rise...

As an example, an f4 infinity shot with Velvia will record 67 MP of resolution. (56 x 69 mm format) At f5.6, 58MP. Compare this with the new P65+, adjusted for f stop, maybe 40 MP max. Stitch a few shots, and it too is a game changer...

Eat that Phase ONE! :-)

And the real beauty is... the 120/220 roll film can be scanned very effectively with the Nikon 9000 and Minolta MF scanners. Too bad they are no longer in production, but they can be had quite cheap on the used market... maybe there is some new Nikon 9000's still around? Anyway, a wonderful alternative to LF and Digital...

sanking

21-Jan-2009, 09:20

BTW, when I look at the results available with a camera like the Canon G10, which has a sensor about 7mm wide, I wonder if the future of digital is not more in the small sensor rather than large sensor size. If you compare an image made with the Canon G10 to one made wiht a 12mp 5D (flull sensor, 36mm wide) or 15mp 50D (APS sensor, 22mm wide) there is precious little difference in resolution. Overall image quality of the Canon G10 iis clearly not as good as that of the 5D or 50D because of noise and dynamic range but one expects this to improve in the future, no?

Sandy King

bglick

21-Jan-2009, 10:17

Joseph, thanks for the kind words .... and humor :-)

just one minor comment.... agreed their is limitations of the fast 35mm lenses that deliver performance "off the map".... for larger prints, it's limitation is the small format size...however, it's these type lenses that make for the ultimate in IQ for stitched shots... a major contender to LF for static subjects. With the newer PS "merge", the multi capture process has become a breeze vs. 5 years ago... another case of technology trumping our "old school" methods. And by old school, now I refer back to just a few years :-)

> BTW, when I look at the results available with a camera like the Canon G10, which has a sensor about 7mm wide, I wonder if the future of digital is not more in the small sensor rather than large sensor size.

BINGO!! Sandy, you nailed this one! It was no joke when Mike R at the Luminous Landscape compared a 39 MP back shot with a digicam (I think G10?) and posted them side by side, and the results were not too far apart. Granted it was a biased representation, but the fact a $400 "system" can even "compare" to a $60k system speaks volumes about the biggest shortcoming of increasing format size, which is the basis of this thread...

apt. diffraction
and
1/R

Yep, as s/n ratios improve, higher density sensors work in concert with these two issues, vs. larger formats, which work in opposition to these imaging laws. Very sad, huh.. AND, what your statement also supports is.... stitched small sensor shots represent the biggest bang for the buck for the ultimate in IQ, as they also benefit from the inherent resolution efficiency of the smaller format!

Your comment also is the lead-in to the Sheldons questions about DOF / resolution with increasing format sizes.... which IMO, is the culmination of this entire thread, and what really matters to most of us......

This is specially true, now that film grain has become a non-issue with the current crop of films AND digital grain / noise removal. 15 years ago, you were forced to shoot one format size larger, when printing LARGE, as often the smaller format would show too much grain, making IQ suffer....even though sufficient resolution existed in the smaller format. Those days are OVER!!! This also supports our position of the Mamiya 7's nearing 4x5 IQ ! As the combination of the diffraction limited lenses and 2 f stop savings allows such a featherweight to compete head-to-head with the heavyweights...

andress007

21-Jan-2009, 10:22

i'm/was 300 dpi prints, 4x5 drum scan etc. type of guy.

Just for joke I downloaded 7 MB jpg file from 21 MP Canon d1s, and up-sized it to 40x60 @ 150 dpi in old Photoshop 7 and sent to guy who prints on Epson 44''. This guy prints only from jpg's files and only @150 dpi from 8x10'' to up to 40''x120'' claiming that where is no visible difference to printing larger than 8x10 from tiff's over jpg's files and 300 dpi over 150 dpi.

Guess what? When I got my 8x10 print (just small crop from center of up-sized 40x60'' jpg file from Canon) my socks was blown off.

Visually the quality of 150 dpi print from 21MP jpg Canon camera was at least the same as my 300 dpi 30x40' prints ' from 4x5 drum scans. Probably using the loupe I would find the difference, but by naked eye the digital print was as good as my old print from 4x5 slide drum scan.

Why I still use 8x10 camera and upgraded from 4x5 to 8x10? I think the camera itself is important factor then making the portrait. The big old style wood camera have very positive influence to the person in front of the big lens and contribute a lot to impression of the person.

My dream is to have 8x10 digital back in size of 8x10 film holder: one side is 8x10 size sensor another side is 8x10 1600x1200 touch screen.

One of the biggest advantages of digital is immediate feedback on laptop screen to evaluate the lighting, focus etc which is not possible or difficult with polaroid (too slow, small etc)

Anyway everything - film or digital - is just a tools to create something which could be later treated as art or as crap.

Emmanuel BIGLER

21-Jan-2009, 10:40

doesn't the scaling of formats inversely parallel the required aperture for DOF to the point where changing the format size doesn't change the system resolution?....
....I know the math doesn't hold up exactly true, but isn't it an approximate rule of thumb?

Good point. Rules of thumb are not difficult to find but with some restrictions.

Rule of thumb#1:
How does the best f-number change with format ?
This was discussed before, if you consider standard lenses from 35mm to 8x10", you make a compilation of the reported best f-number and the scaling for standard focal length (=diagonal of the format) law is roughly

N_best = f(in mm) / (8 mm)
this rule matches the following list
N=5,6 for the 50 mm in 24x26 format
N=8-11 for the 80 mm in 6x6
N=11-16 for the 100mm in 6x9
N=16-22 for the 150mm in 4x5
N=22-32 for the 210 in 5x7
N=32-45 for the 300 in 8x10

May be those figures have to be updated for top-notch modern standard lenses for film like the apo-sironar-S or apo-symmar-L, and certainly do not reflect the best f-number for 'digital' lenses. But consider that the best f-number simply scales with the diagonal of the format, imagine N_best = f(in mm) / (11 mm) for top-notch lenses, the situation is the same.

Rule of thumb#2:
The classical geometrical DOF model is based on the hyperfocal distance, H = f^2/(N*c) where "f" is the focal lenths, "c" is the acceptable circle of least confusion., "N" the f-number

The choice for "c" is critical and source of many misundestandings but consider the classical...
rule of thumb#3 c=f/1720 for 2 minutes of arc as the resolution limit for a 8x10" print viewed from a distance of one foot.
1 minuet of arc is probably what jet-fighter pilots can see ;) not me

Combining rules #1 for the best f-number N = f(in mm)/(8 mm) across various formats, #2 for the hyperfocal distance and #3 c=f/1720 for a the choice of "c", we eventually get something a bit provocative (an already posted here):

best H = 1720 x 8 mm = 13.76 metres ;) for all formats with standard lenses at the best f-number !

Once H is fixed, the geometrical DOF limits have no choice but complying with the geometrical formula 1/p_{12} = 1/p {+ or -} (1/H).(1-f/p)

This rule is probably hard to accept because it implies that the total number of resolved points in the image is independant of the format ! OK, consider that a real image is not made of circles of confusion at the limit, and that only small portions of the images reach the limit of unacceptable sharpness defined by "c". Within the portions of the image that reach the optical and sensor limits, the usual rules apply ; in portions of the image that can be considered as diffraction-limited, the minimum, really ultimate, detectable feature has a period of about 0.7 N in microns. This period is independant of the format. Since the best f-number "N_best" increases with the format, the size of the minimum detectable period increases proportionnaly to "f" like the geometrical value for "c" above, and again, if all lenses were diffraction-limited, and images perfectly in focus, there would be no gain in the total number of resolved points across formats !!!

So what is wrong ? a tentative list of objections against the previous derivation

- we did not discuss what happens with wide-angle lenses, a field of application where the view camera produces outstanding results; and what happens with long focal lengths?

- we did not take into account film resolution-> OK large format wins because grain and film resolution is no longer an issue in LF

- we did not take noise into account -> silicon sensors require such a tiny surface in order to record good images that the analysis is biased ...

- we did no take into account all secrets tricks used by manufacturers of digital cameras and backs to boost the quality of the image by software : cheating with the MTF of the lens, secretly combining pixels and smart sharpening algorithms... by definition this is proprietary and kept secret, so there is little to say...

If we want to compare the ultimate detection capability of film versus silicon, we have to dig in old textbooks about the equivalent quantum detection efficiency (DQE) of film ; good ol' tri-X was credited of a DQE of 0.5 % at the end of the as century ; modern tabular-grain films probably reach a DQE of a few percents, professional digital backs with a Bayer filter already reach something like 15-20%, and top-class monochrome sensors for space applications reach a DQE of 80%.
Whereas there is probably no future for better films with a better DQE, we could imagine to improve the DQE of photographic sensors up to 50%.

However I am deeply convinced that scaling laws for the best f-number still applies for digital camera lenses.
Simply because the diffraction of light does not scale with the focal length and the format whereas residual geometrical aberrations do. The consequence is a mandatory scaling law in the genre of N_best = f / something, the value for this something is still to be found by comparing all available digital camera lenses !

So I do not expect sub-35mm sensor formats to be able to compete with full-frame and medium format silicon sensors, simply because I do not believe in diffraction-limited lenses opening at f/1... the extrapolated value for the be f_number a focal length of 8mm !

- we did not take into account mixed effects of diffraction and geometrical defocusing. Beyond the best f-stop the classical geometrical DOF model fails.. but it fails gently and gradually, not abruptly. In the far out-of-focus areas of the image, geometrical defocusing still rules hence the geometrical model holds. But the sharpest parts of the image become less sharp... to me this is not a major objection againts the good old DOF model, at least to figure out simple rules of thumb.

Another point regarding tilts and the classical Scheimpflug rule across various formats. Again if we consider a purely geometrical model, to me things are simple.
When tilting, you can get the same DOF with small silicon sensors with the appropriate f-number, say f/5.6 instead of f/16 in 4x5",., but since the focal lengths are so small, the required tilting angles will scale down like the focal length. This is a purely geometrical effect.
So this makes a manual & visual setting very difficult on a ground glass, but not so difficult in the live-video mode on a computer screen if your tilting controls are very precise. But be prepared for tilting angles of one degree or less...
Hence the solution for maximum DOF with digital capture on small sensors is to ignore Scheimpglug definitely and stack/merge as many images as required for recording various planes of sharpness in the object...

bglick

21-Jan-2009, 11:46

Emmanuel, GREAT POST!!!

Some comments....

> N_best = f(in mm) / (8 mm)
this rule matches the following list
N=5,6 for the 50 mm in 24x26 format
N=8-11 for the 80 mm in 6x6
N=11-16 for the 100mm in 6x9
N=16-22 for the 150mm in 4x5

I agree with this in general, and you have correctly pointed out, as modern lens design has improved, the variance from this old "standard" has moved greatly, and we have many more designs that are targeted to specific tasks... a previous poster found a vintage LF lens that performs near diffraction limited 135mm lens at around f7... and as you correctly mention, the newer LF lenses, such as the SSXL 150 is optimized as low as f11!! This is why lens makers provide MTF data on lenses, so we can see where the lens was optimized, as it relates to f stop and focus distance. For best IQ, match the right lens to a given task...

Your general assessment of H = 45 ft is solid.... as these are non macro lenses you discuss, and this focus distance is a mid point, between a near focus and infinity focus. When you design a lens to perform well at both distances, your design criteria is mid point...then the errors fall equal on both sides. This is why "portrait lenses" exist, as the lens designer optimized the lens for a single task, with a single focus distance, producing max. resolution at THAT distance only. Of course, as fl's go to the extremes (WA and tele), this does change a bit, but not worth mentioning here....

> So I do not expect sub-35mm sensor formats to be able to compete with full-frame and medium format silicon sensoirs, simply because I do not believe in diffraction-limited lenses opening at f/1... the extrapolated value for the be f_number a focal length of 8mm !

Yep, you have correctly pointed out the current brick-wall small sensors are facing, to get to the next level.... optics! The current f2.8 standard must be trumped....heck, its only been a few years since this rage has started, give these makers time. Something we have never seen before, Wall Street money, combined with optical design software with huge market$ that await. Considering 1/R and apt. diffraction are their demons as well, you know these makers are working to continually work in concert with these restricting imaging laws.... At this point, it's anyones guess "if" or "when" this might happen. But, everything has limits, I am not suggesting an APS digital sensor will trump a large MFDB... my point was, (confirming Sandy's suspicion) there is still room for improvement at the small sensor end.

> But the sharpest parts of the image become less sharp... to me this is not a major objection againts the good ofl DOF model.

I agree, however, the problem with the 1800's DOF model, is there is no ceilings on resolution...it does not respect 1/R, which can really fool people today. You can't just randomly toss in any cc value you want, without a solid understanding of the lenses, f numbers, recording MTF, and 1/R... The reason these two critical formulas never joined up....is quite obvious, DOF formula was created 100+ years ago, whereas 1/R in 1970. But as you correctly point out, the basic premise of how lenses DeFocus from the point of exact focus is the value of DOF / Hyperfocal calcs.... You also must be careful applying DOF calcs to the specialty lenses, such as portrait, macro, etc. (just mentioning the obvious)

> When tilting, you can get the same DOF with small silicon sensors with the appropriate f-number, say f/5.6 instead of f/16 in 4x5",., but since the focal lengths are so small, the required tilting angles will scale down like the focal length. This is a purely geometrical effect.

Excellent observation.... However, there is one competing factor here that reduces the potential benefits. As a general rule, the smaller the image circle per same fl, the higher the aerial resolutions, and higher MTF's. To enable tilt (or rise) on small sensors, you must enlarge the image circle. While I agree small tilt angles scale with fl, the larger size image circle requirements will slowly eat-up the potential gains of tilting. The image circle sizes are critical to resolution. In addition, the tilt precision will be so demanding, the opto mechanical costs will become so great..... any potential gains will be outweighed by cost and build complexity. The fact that ultra short fl's already have tremendous DOF, tilt is not a high on the priority list for camera makers in the small format arena (IMO). More importantly, with the advent of Focus stacking software, these small gains you suggest are now only significant with non static subjects....

I don't think this answered Sheldons question in the method he preferred..... I will try to respond later today using the same conventions this thread has taken on...

bglick

21-Jan-2009, 11:59

> This guy prints only from jpg's files and only @150 dpi from 8x10'' to up to 40''x120'' claiming that where is no visible difference to printing larger than 8x10 from tiff's over jpg's files and 300 dpi over 150 dpi.

Sheeesh, lots of issues in your post...but I will address this particular one... 150 dpi = 3 lp/mm, assuming no losses in the printing process. If you feed the printer 300 dpi, there "should" be a gain in printing resolution.... but, this is where details come into play....

1) this assumes, the operator is printing at high enough dpi to lay down the added data

2) this assumes the paper and ink combination can exceed recording 3 lp/mm per mm... many non coated fine papers can NOT!

3) this assumes, you are viewing at normal distances, say 30", 3 lp/mm on paper is already a high standard, as its beyond what the eye can resolve at that distance.....more resolution would not easily be discernable, unless there was extreme lighting on the print.

> My dream is to have 8x10 digital back in size of 8x10 film holder: one side is 8x10 size sensor another side is 8x10 1600x1200 touch screen.

If you followed this thread, you will learn, a sensor this size will be greatly limited by apt. diffraction due to the long fl and higher f stops used on 8x10... its in conflict with the laws of imaging, hence why we will never see this product.... However, a 8x10 scanning back would be interesting....but this requires static subjects, in which case, its easier to stitch with off-the-shelf DSLR, better results and less back pain....

bglick

21-Jan-2009, 15:36

Moving this thread to the DOF / print size issue Sheldon asked about.... which answers the "what format" question we all struggle with... regardless whether its a purchase decision, carry decision, cost decision, its a major issue for all landscape / architectural photogs...

First the disclaimers.... many people like larger formats for the big ground glass, the slow technique of view cameras, the beauty of a Big Honkin Ebony 8x10 sitting on a tripod, etc. This discussion does not address any of those likes / dislike issues. It only pertains to how DOF and its associated diffraction effects OFR (On Film Resolution) and final print sizes.

The recorded MP's of resolution described previously were ideal in comparing formats of all different sizes / types. However, the MP's value is a bit deceiving for some, as ultimately, it's the final print size that matters. Since it takes 4x the recorded MP to make a print 2x as large, while holding the SAME OPR (On Print Resolution), the recorded MP's doesn't deliver the ultimate information needed for those who make prints as the final product. So, I will express how the effects of 1/R at different format film sizes, will effects the max. size final print, at a given resolution. This assumes regardless of the size of the print, it will be viewed at the same distance, which today, seems to be commonplace as everyone has become resolution obsessed. Till the prints become 60" +, whereas often you are forced to view at a greater distance to fill your field of view to "take in" the entire print. Let's use an aggressive 5 lp/mm to the printer... with printer losses, you may yield 3 - 4 lp/mm to the final print... still a VERY high standard!

I will use 3 formats, 4x5, 8x10 and the little gem previously mentioned, Mamiya 7. Lets use color film at an avg. MTF of 60 lp/mm (expect better results with B&W). Format sizes..., I will use 4x5 at 90x120 and 8x10 at 180 x 240 to keep these two at exactly 2x, or 4x area. Therefore, for same composure and DOF, you always double the fl for 810 vs. 45, and also double the f stop, pretty simple.

The M7 will have to stand on its own unique size, not conforming to the 2x vs. 4x5 rule. But since it has a 1.23 aspect ratio, nearly identical to 4x5's 1.25, it makes for an ideal comparison. Since all the aspect ratios are the same, I will express the print size on the horizontal dimension only for all films. With a 89mm film diag. on the M7, the increase in fl to 4x5 is reduced to a 1.7x factor, as well as the increase in f stop.

And of course, we are making the assumption your scanner can extract all the data from all the formats. This post also assumes you understand basic DOF premise, as it relates to format size...i.e. same composure with different format sizes requires proportional increase in f number, vs. lens fl increase.....which will always yield the SAME resolution at EQUAL size final prints. (all else being equal)

First, we display LF in all its GLORY -

SCENARIO #1 - Infinity focus or flat plane subjects....

M7 = f4 1/R = 52 lp/mm

52 * 69mm film / 5 lp/mm print / 25.4
= 28" print on Horiz.

I won't repeat the math from here on...

45 = f11 (a lens optimized at f11) = 39" Horiz.

810 = f11 (for illustration purposes) = 79" Horiz.

Although there is only a few lenses on 810 that have great performance, I used it to demonstrate the expected 2x increase in print size when doubling the format. You can adjust numbers accordingly, maybe f16 or f22 is more realistic with the lenses you use. Anyway, the obvious message here is..... with NO DEPTH, LF film still rocks the imaging world, nothing compares - SLAM DUNK!

Next, the sad reality of the DOF, and how the imaging laws rear their ugly head for scenes with depth. I will offer a Mild DOF scene scenario and an extreme DOF scenario, as the numbers vary greatly. Each time, always increasing the f stop by the same factor the lens fl increased.... Since the M7 lenses are diffraction limited at low f stops, we can use their true values in 1/R.... as well as the 45 / 810, as at such small apertures, most of the modern lenses are diffraction limited also...

SCENARIO #2 - Mild DOF (rez holds up relatively well)

M7 f9.4 = 24" Horiz. print

45 f16 = 35" Horiz. print

810 f32 = 50" Horiz. print

Now, the sad news, where most of us end up, more extreme DOF scenes..... and addresses Sheldons question about f32 on 4x5.

SCENARIO #3 - Extreme DOF

M7 f19 19" Horiz. print

45 f32 25" Horiz. print

810 f64 49" Horiz. print

This is why I will never sell my 8x10 gear.... as apt. diffraction attacks 4x5 and 810 equally with extreme DOF, hence the incredible value of added film Real Estate area... But at the smaller end, M7 due to the its smaller f number is more 1/R friendly, and nearly matches 4x5....and when you consider the extreme precision of the M7 system vs. 45, and it's ultra high contrast lenses (not accounted for in this calculation), I will agree with Sandy, M7 actually does match 45 in the extreme DOF scenario, (color film) hence why I call this camera system a gem..... I carry mine in a waste fanny pack...crazy, huh.

Now, before the machine-gun fire ensues.... keep in mind, these are for the same viewing distances, and a very high standard of OPR (On Print Resolution) If you increase the view distance by 2x, you can increase the horiz. print dimensions by 2x, and still hold the same perceived resolution. If you decrease the OPR requirements in half, you can also increase the print sizes 2x.

Also, the lighting you view prints under, is another huge variable not mentioned, which can also deceive many when comparing prints in galleries vs. their homes, etc. The MTF of the eye also plays a critical role in perceived resolution, as it too is effected by it's f number... as it has a fl and a varying apt.... but that's another thread. This is one of the reasons you hear a lot, "that's not what I see" comments. Just making it clear, the print resolutions above is just ONE factor in the imaging chain... although often the most critical one.

Sheldon, does this answer your question?

andress007

21-Jan-2009, 15:51

bglick, I don't know how this guy print, but I sent him jpg @150 dpi and got back quality about the same as my 300 dpi tiff prints.

where is no substitute for square inches of recording media: for digital or for film - it doesn't matter - the larger the better. That's why they made 35 mm film cameras and up to 20x24 film or bigger cameras, and that's whey they make 1/3, full 35 mm and 51x38 digibacks and probably soon 6x6 or even 4x5 digi.

For sure they are different cameras for different jobs and different situations. But always 4x5 film will blow 6x6 and 35 mm film, and 51x38 digital will blow 35 mm digital.

Sheldon N

21-Jan-2009, 21:04

Sheldon, does this answer your question?

Yes thanks everyone, it certainly helps. I guess it's not quite as simple as a "rule of thumb".

Thanks for the kind words on my pics, too. It's funny that I read this thread on high resolution film and digital images with great interest, when the majority of my photos end up getting displayed as 1000 pixel wide jpegs on the internet. :)

I don't have to do a "Michael Reichman double blind print test" to know that there's no difference between pictures taken with my Canon G10, 5D, or 4x5 Arca Swiss when it comes to Flickr! :p

Tim Povlick

21-Jan-2009, 21:47

Interesting thread...

A question if I may. The attached is a spot diagram that shows on/off-axis performance of an 80mm-f/7,5 lens. The black circles indicate the size of a diffraction limit spot. On some wavelengths (green in particular) the spot diagram shows it is well inside diffraction limit. It looks as if one could use a green filter some b&w film and 'beat' diffraction limit. What did I miss.

_ .. --
Tim

rvhalejr

22-Jan-2009, 07:18

DQE == quantum detection efficiency
(apparent english order: Detection Quantum Efficiency)

Whereas there is probably no future for better films with a better DQE

1.) 20nm polymer film crystallization (attached image)

"Organic and Polymer Photovoltaics"
ref: ...mrc.utexas.edu/NSFworkshop/Presentations/mcgehee1.pdf

2.) Ag depth of ~13 nm

"Polymer photovoltaic devices with highly transparent cathodes"
ref: ...ntur.lib.ntu.edu.tw/bitstream/246246/87082/1/41.pdf

3.) Current T-Grain Films

....en.wikipedia.org/wiki/Tabular-grain_film

Emmanuel BIGLER

22-Jan-2009, 07:35

the size of a diffraction limit spot

Hello !
Well we are drifting a bit off-topic but let me make a comment !

Well the only problem I see is that I do not know what is the diameter of this diffraction spot ;-) as you probably know, a diffraction-limited spot has no sharp edges, so it is somewhat arbitrary to define its actual diameter.
Lord Rayleigh has a definition, and since He Was Lord Rayleigh, for more than a century people continued to use His Definition ;)

Well assume that we have a reasonable definition for this diameter, for exampe the full-width at half-maximum of the intensity per square area (this is different from the optical density on a film !).
Usually, optical simulations considering white light go up to 0.7 microns, the actual limit of what the human eye can see. If you stop the simulation to 0.5 microns, in the green region of the spectrum, the diffraction spot is smaller and the lens performance, better. And if you reduce the range of wavelengths actually in use, you also improve performace in terms of residual chromatic aberrations.
I have used a long time ago a high performance process lens made by Cerco ( France) for photomask fabrication with high-resolution silver-halide plates ; the lens had a permanently attached green filter. The lens Was actually diffraction-limited @f/4 but for a narrow range of magnifications, I do not thinks there would be any interest for photography, but who knows ? :)

Regarding the spot diagram method and the definition of the size of a combined aberration/diffraction spot, one of the reasons why engineers like the MTF curve so much in their simulations is probably as follows.
If you make a simulation neglecting diffraction effects, e.g. to compute geometrical aberrations, you eventually end up with infinite values for light intensity per square area detected in the image plane. For example a pure spot of spherical aberration has an infinite intensity per square area at the centre.
So it is meaningless to define the full-width at half maximum for a quantity wich is infinite at its maximum !
Hence, you have to find someting else ; another criterion mentioned in old textbooks was the encircled energy which is not infinite, it is the integral of the light intensity per square are, inside a given circle. This gives a finite result. So you can define the size of the spot by the diameter that will encircle, say, 90% of the total energy in the beam ; doing so, you avoid the problems of manipulating infinite quantities, but this is still an arbitrary definition for the diameter of an image spot.

Eventually the MTF approch is even better since you can define the MTF for a simulation where diffraction is neglected ; like the encircled energy, the MTF is finite and can be computed even if the intensities per square area are infinite.
And you can combine both aberrations + diffraction of course.

The advantage of the MTF simualtion is that there no longer any need to define an arbitrary diameter for a spot, hence this reduces some sterile controversies between lens manufacturers ;) too bad that the MTF approach is so difficult to figure out.

There is a nice tutorial by Carl Zeiss recently published on this subject, the author is H. H. Nasse and there is little to add to this tutorial written by an expert.
http://www.zeiss.com/C12567A8003B8B6F/EmbedTitelIntern/CLN_30_MTF_en/$File/CLN_MTF_Kurven_EN.pdf
This is a companion article to the last issue of Zeiss Camera Lens News issue # 30, Dec. 2008
http://www.zeiss.com/C12567A8003B8B6F/EmbedTitelIntern/CLN_30_en/$File/CLN30_English.pdf

Emmanuel BIGLER

22-Jan-2009, 07:48

... 20nm polymer film crystallization ... Ag depth of ~13 nm ... Current T-Grain Films

Sensitive Polymer & al. research news : many thanks for the references : I appreciate !

Yes ! Analogue and Photo-Chemistry Rule ;)

If our readers are not convinced that Analogue Imaging & Photo-chemistry Actually Rule : figure out how your silicon image sensor is manufactured :D

Including the last sensor, 12 Mpix by Sony for mobile phones and a pitch of 1.7 microns for the pixels !

rvhalejr

22-Jan-2009, 08:34

...
N=5,6 for the 50 mm in 24x26 format
...

S/B N=5,6 for the 50 mm in 24x36 format

mcfactor

22-Jan-2009, 09:05

One aspect that is being ignored in this post is the greater tonality that you get as you increase film (or sensor) size. While I understand that resolution is negatively affected by smaller aperatures, the tonality of the image is not. So, while an 8x10 negative taken at f/90 may not have much more (if any) resolution that a medium format digital back taken at the optimal aperature, it will certainly look richer and have deeper tones. Which is really why many people continue to use large format.

I realize that this post is about resolution (and in that regard it is very interesting), however the underlying implication is that with higher resolution backs, large format film cameras are becoming obsolete. And I think it should be noted that resolution is only part of the decision to use large format.

Nathan Potter

22-Jan-2009, 09:48

Emmanuel, I regret that I've not taken the time to study this thread thoroughly but the above post, Sony 12 Mpix mobile phone, from you caught my eye. A 1.7 um pitch implies a pretty tiny pixel size, far under the size of a circle of confusion that one could expect from a cell phone! Be this as it may; I'm intrigued by the possibility of sampling a circle of confusion using multiple pixels (that is sampling a point spread function) then converting that information to a higher MTF equivalent using a sophisticated signal processing algorithm. In more concise words I'm trying to say one may sample, for instance, a gaussian point spread distribution in X,Y space and convert the information to a Fourier distribution, in X,Y space in order to increase the resolution of the image. Of course I realize after glancing through the Zeiss article you so kindly referred to above, (thanks by the way), that these point spread functions are very complex due to the complex lens aberrations across the field of view. In any event the notion of such signal processing is intriguing. Are you aware of any such digital signal processing activity along these lines? This could lead to an advantage in producing pixel pitches that are smaller than the lens resolution limit as discussed early on in this thread. More interesting would be the possibility of beating the pervasive 1/R relation so often discussed by bglick. (I think I'm imagining this correctly).

Nate Potter, Austin TX.

bglick

22-Jan-2009, 10:11

> taken at the optimal aperature, it will certainly look richer and have deeper tones. Which is really why many people continue to use large format.

A good point...this was a disclaimer I forgot to mention in the resolution posts.... IMO, your point is "sometimes" valid. If you look at the curves for each film type, you will see many of the color trannie films have limited tonality potential throughout their exposure range.... very similar to 12 bit digital capture, which records tonality on a linear scale.... with the top stop of exposure recording half of all the available tonality steps. The next stop down records half of the remaining steps, etc, etc.... this is why as exposure latitude of the sensors increase, they must offer more A/D conversion head room... 16 bits will be optimum...who knows when this will be common place....

although I have not looked recently, I think B&W neg films strongly supports your position...

Also, as users get better digital manipulation skills, they tend to expect less from the capture and modify the digital image to overcome all types of shortcomings... in the mid 90's, Photoshop was like a kiddie program vs. what we have today. Technology is pushing digital in very aspect, but film sales keeps declining. I just hope the current crop of film is made for the next 10 - 15 years min...

bglick

22-Jan-2009, 10:33

> Not true, last years film sales for 4x5 increased by 40% (according to reports at the Photokina 2008 show).

This is the most exciting film news I have heard in a long time, thank you for sharing.... yeee ha!

As for film camera sales...although there is more makers, these are often cottage type industries, producing very low numbers of cameras. I know Toyo went from 33 workers in 1995 to 2 workers today... that speaks volumes.. I think the best chance of LF films holding ground is the newbs who enter.... since most high volume shooters went digital, we need a greater number of low volume shooters who seek great IQ. The lack of NEW and supported scanners at cost effective prices does hurt this paradigm a bit.

> Ever see a 10ft print from 8x10....a p65 doesn't have a chance and must interpolate. Ever see a 10ft print from 8x10....a p65 doesn't have a chance and must interpolate.

Damn it, not enough people buying 10 ft prints!!! :-) Anyway, the rest of your points are valid....but IMO, the next big wave will be the low cost 24MP DSLR's.... everyone seems to forget about stitching. A handful of stitches go a loooong way and can easily surpass 4x5. This leaves 4x5 supremacy with non static subjects. Till now, stitching IMO has not been as embraced as its resultant outcome would suggest. The only reaons IMO is, lack of knowledge and the previous cumbersome software to merge the images AND the nodal point issues of capture were a bit too techie for some. With PS's new PhotoMerge, its a game-changer again......now you snap 5DSLR 20 + MP shots, and whamo, it blows me away every time I do it... most of the time, I don't even use a tripod anymore. Once I used an 8MP digicam (which is all I had with me) took 10 shots of a scene, hand held, photomerged them, and the final output was stunning at 40"..... if someone told me this 10 years ago, I would have thought they were insane.... The good news is.... film also benefits from many of the digital benefits....but tools like Photomerge bridges the gap between capture and desktop work.... and its the capture that makes film vulnerable....

BTW, how are 120/220 sales? Sometimes you wonder if both Fuji and Kodak can survive in the color market. I think if one closed, the other would survive way longer than if both continue. If someone is a stock holder, I am curious if the annual reports list these specifics?

mcfactor

22-Jan-2009, 10:39

I was responding to exactly what you seem to be angered by, van camper. I said that the "underlying implication (of this thread) is that ...large format film cameras are becoming obsolete." I did not say that large format is dead or dying in any sense. My point is that we should also factor tonality into our discussions of different photographic mediums. I also mentioned in the beginning of my post that tonality is increased with higher quality digital backs as well as larger-format film. I was explicitly trying to avoid describing one as better than the other. What I did want to do was give some reasons for the continued use of large formats.

bglick

22-Jan-2009, 11:32

Argggggg.... sorry guys, a typo.... I can't go back and edit the post, its too late, but here is the fix....

I wrote this....

SCENARIO #3 - Extreme DOF

M7 f19 19" Horiz. print

45 f32 25" Horiz. print

810 f64 49" Horiz. print

The correction is, the 3rd line should read,

810 f64 32" Horiz. print

further emphasizing how diffraction beats the pants off resolution..... while 810 still holds an edge, and when you need big prints, you pursue every last bit of detail.... but when you consider 810 can only make a print 1.3x larger than 4x5, and 1.7x larger than M7 (32"/19").

Again, this identifies the achillies heel of the BIG formats, i.e. extreme DOF. A lot of added size n weight of the gear vs. the marginal gains. No biggie for the studio guy, but sure is for the backpacker :-)

Emmanuel BIGLER

22-Jan-2009, 11:41

From Nathan :
the above post, Sony 12 Mpix mobile phone, from you caught my eye.

Sorry, I should have referenced what I said.
About the the 12 Mix Sony camphone sensor, I found this at Sony
http://www.sony.net/SonyInfo/News/Press/200811/08-144E/index.html

and the pixel size is mentioned as "1.4 microns" but there is always a doubt wether people mean the pixel aperture or the pixel pitch, but 1.4 (not 1.7 as I mentioned above) is the actual pitch that you can reverse-engineer from the aspect ratio, the total number of pixels and the diagonal size.

So let's go for 1.4 micron as the pixel pitch, which is really amazing !
The sampling theorem demands 2 pixels per minimum period, i.e. 2.8 micron.
If we take 0.7 micron as the actual wavelength limit for visible ligth, a diffraction-limited lens passes a minimum period of 0.7 N microns.
Hence the f-number of this lens should be 2.8/0.7 = 4 in order to comply with the sampling theorem.Sony offers a lens module (see above web page) with a max aperture f/2.8, so the engineers know their stuff. I doubt that this tiny f/2.8 lens will be diffraction-limited @2.8, but @f/4, nobody knows !
Having used a diffraction-limited lens @f/4 in the past for making photomasks as mentioned above, I seriously doubt ;-)
OK, the comparison is misleading, since my lens was a very complex lens, covering a field of 2"-1/2 x 2"-1/2, a common size of high resolution plates at the time, so a lens designed for 4.2 x 5.6 mm might be much smaller, and can be simpler with aspherical elements, a technology not yet implemented in my Cerco lens !
Anyway, you can't argue that the figures claimed by Sony are nonsense.

Are you aware of any such digital signal processing activity along these lines?

I am not at all aware of the details. But I have discussed those topics of digital pre-processing inside the camera in October 2007 at our large format conference with prof. Süsstrunk of EPFL (the Swiss Federal Institute of Technology, near Lausanne, Switzerland).
She is the head of the Images and Visual Representation Group. She presented very interesting examples on how to use the specificities of human vision in order to optimize and improve the visual rendering of digital data. For example Edwin Land's Retinex models are implemented, there is even a plug-in for the GIMP ;)
Prof Süsstrunk mentioned to the attendees of the conference several developemnts about the "smart grouping" of tiny pixels. So if public labs do that, it is guaranteed that similar research is going on in all R&D departments even if nothing is published.

So I know from this informal conversation (where of course nothing proprietary was disclosed) that the research effort on digital image pre-processing "inside the camera" are huge. Both at the R&D department of the major players like Canon but in all public research labs in the world.

But after this long answer, it is perfectly clear that the diffraction limit is an absolute cut-off frequency and that it is of absolutely no interest to over-sample. Even the guys at the sales dept. cannot argue about it against the engineers ;)
A real lens being not as good as a diffraction-limited lens, it even means that you have some margin with respect to the absolute limit and probably we already have reached this practical limit for camphone lenses.
However from the web page of Prof. Süsstrunk's group, I extract this research topic:
"Super-Resolution Imaging"
http://ivrg.epfl.ch/research/topics/superresolution.html
a related matlab demo :
http://ivrg.epfl.ch/software/index.html
Now regarding my photographic activity in LF, I have no objection using film while at the same time being informed of the progress of digital imaging.
The more we know what digital imaging can do, the better we are prepared to continue quietly our LF activity on film on the basis of good arguments with no fears of being mocked at as old-fashioned guys ;)
But we need film suppliers ! So I am really happy to read that film sales a going up again.

Gordon Moat

22-Jan-2009, 13:45

Emmanuel, recall that some manufacturing processes do not use visible light. When you alter the wavelengths in use, then the lenses used will perform differently.

You are correct that there is a dead zone between pixels. This will effect sensor efficiency. Fujifilm have experimented with a sensor that is more film like, though it is a few more years away from a viable product (if ever). Regardless of ultra small pixel sizes, the greatest sweet spot of performance is still in the 6 µm to 8 µm range, as indicated in a few industry white papers on this (including from Fill Factory, possibly still available from them). Reducing the spacing between pixels can improve performance, and might be another step (Canon touted this advance not long ago).

I recall some Kodak engineers indicating a realistic goal of a roughly 645 sized sensor of about 100 MP as a practical limit. That is not to state that they could not go beyond that, simply that there would be little advantage going beyond that, due to noise, interpolation error, and other issues.

That leaves pixel bunching, for some tasks, as an alternative. Sanyo and others have shown this is very small cameras and camcorders. Groups of four or more pixels are processed together for lower file resolutions, often with the benefit of enhanced sensitivity. This may become a strategy employed for larger sensors, for those times when lower file resolutions meet end user needs.

PhotoShop has been dumbed down in an effort to enhance productivity or simplify operation; this makes it faster for some, and slower for others. I have yet to see a direct correlation to changes in PhotoShop altering creativity. Many things possible in PhotoShop 3 or 5 are now simply faster. In other words, I have seen no digitally manipulated images in the last year which could not have been done with an older version of PhotoShop; I do acknowledge that certain digital manipulations can now be done faster. Software knowledge, skill, and quickness are not substitutes for creativity. You still need the ideas prior to finding a way to express them.

Which brings us back to film. If film is indeed obsolete, as some claim, then it implies that film images are no longer relevant. Taken to an extreme, it further implies that the images of the past, from film, are no longer relevant.

So how can I possibly use film, in the face of all this technology? One answer is that I deliver digitally; in fact, I always have delivered that way, starting in college in 1994, and continuing into a creative profession. Another answer is that there is a way of working with certain cameras that requires a different approach than direct digital capture. Whether that is upside down images on ground glass, or clunky old cameras, the approach can alter the interaction with subject or scene. To some, they prefer the approach (or freedom) of using a DSLR, MFDB, or tethered shooting, and those are no less valid choices than using a film camera.

We run into problems when we want to reinforce our choices, or quantify our choices. We can define for ourselves a basket of criteria of needs, then slot an imaging system into those needs, and in that process identify our ideal imaging solution. When that does not hold up is when we try to apply that to others, or when some seek to demean the choices of others (intentionally or unconsciously).

I can go to a subject or scene, and then draw it, paint it, or photograph it. Drawing and painting are hopelessly obsolete, low resolution, low tech, and at times downright cheap. Yet I find an elegance in simplicity. To me, only using a view camera comes near the approach of drawing or painting; the ground glass is my sketch pad and canvas.

Ciao!

Gordon Moat Photography (http://www.gordomoat.com)

bglick

22-Jan-2009, 14:20

Rakesh Malik

22-Jan-2009, 15:05

[quote]
> Many things possible in PhotoShop 3 or 5 are now simply faster. In other words, I have seen no digitally manipulated images in the last year which could not have been done with an older version of PhotoShop;

hmmmm... hard to grasp this....

Let's see if you can grasp this one: many != all.

PhotoMerge, Auto Align Layers / Depth of Field Blending, Content Aware scaling, 3d enhancements.....I could go on and on....

You ought to take a look at what the movie production studios have been doing. These features made things that people were already doing easier, so obviously it didn't make anything previously impossible suddenly possible.

PS is revolutionizing the way we think about Image Capture....

No, it isn't. It's still catching up to the film industry.

In fact, when I attended a presentation put on by Maxon and Adobe, demonstrating the capabilities of Maxon's 3D software in combination with Adobe's audio, video, and compositing software, I couldn't help but wonder why Photoshop was so far behind.

IMO, the EXACT opposite is true... Us LF photogs can ONLY dream of the day when a LF print garners the same respect as an oil painting of the same scene.... sad but true... the ratio of galleries in the USA, paintings vs. Photography is probably 500:1 or greater. This speaks volumes on the publics perception of "what is art" .....

IMO it speaks volumes about how diluted photography has become as an art form because of the legions of snapshooters out there using their high-tech toys and publishing their drivel for the world to see, and only because they can.

"If at first you don't succeed, lower your standards."

That's long been the apparent mantra of government contracting, but apparently it's contagious.

rvhalejr

22-Jan-2009, 15:06

> This speaks volumes on the publics perception of "what is art" .....

I saw a lot of zooming in and out at the inaugural but have not seen one really nice LF picture yet from the capitol dome (an AA shot high up). Hopefully there were at least two 8x10s up there.,.

bglick

22-Jan-2009, 15:39

> You ought to take a look at what the movie production studios have been doing. These features made things that people were already doing easier, so obviously it didn't make anything previously impossible suddenly possible.

OK, I should have added.... making these powerful tools available at a price point the avg. photog can afford....i.e. $200 vs. $200M :-) Like most technology, it filters down to mainstream over time, at affordable prices with simple to use interfaces. I would agree, in many ways PS is way behind in certain areas of graphics software...that's what happens when you have no major competitors...

Rakesh Malik

22-Jan-2009, 16:50

OK, I should have added.... making these powerful tools available at a price point the avg. photog can afford....i.e. $200 vs. $200M :-) Like most technology, it filters down to mainstream over time, at affordable prices with simple to use interfaces. I would agree, in many ways PS is way behind in certain areas of graphics software...that's what happens when you have no major competitors...

It's pretty frustrating that there's so little competition for Photoshop, isn't it?

On the bright side, at least there are several competitors for Lightroom floating around.

Gordon Moat

22-Jan-2009, 18:02

> Which brings us back to film. If film is indeed obsolete, as some claim, then it implies that film images are no longer relevant. Taken to an extreme, it further implies that the images of the past, from film, are no longer relevant.

HUH? You can't be serious about this? Who is implying any of this?

I hear or read this on a weekly basis, and that has been going on for many years now. Sad and true. Gladly I am finding people more open minded about this now than I did a few years ago.

> Many things possible in PhotoShop 3 or 5 are now simply faster. In other words, I have seen no digitally manipulated images in the last year which could not have been done with an older version of PhotoShop;

hmmmm... hard to grasp this....
Why? Simply show me an image that could not have been created in PhotoShop 5, and it disproves what I stated.

PhotoMerge, Auto Align Layers / Depth of Field Blending, Content Aware scaling, 3d enhancements.....I could go on and on.... PS is revolutionizing the way we think about Image Capture.... as well as, how we manipulate images.

All productivity changes. Merging, alignment, blending, selective scaling and more could be done starting with PhotoShop 3 and layers. Accurate colour control starting in PhotoShop 5.0. The 3D texture mapping is one of the few changes, though it was possible to control texture maps in PhotoShop 3, and I recall sending those texture maps to Alias Studio many years ago. The biggest change in the 3D realm within PhotoShop is support for file types not previously handled directly in PhotoShop.

The end result is still a flat 2D image. Whether it took longer, or was more difficult for some people in older versions, is a separate aspect. Look, this is progress from Adobe, to make some aspects easier or more accessible, and that is a good evolution of PhotoShop. In some ways that helps, and in other ways it slows down some procedures.

Of course, no software develops a Master Plan. But all the imagination and creativity in the world, won't allow you to reach a given final product, without the proper tools. And it's knowledge of the tools that enables us to imagine "what's possible". It's the same in every craft....the premier craftsman is someone with a mix of creativity and solid understanding of their tools.

Actually, Adobe does have a Master Plan for PhotoShop, and all their other software. I have three friends who work at Adobe, and I hear about things often. Now if you meant something else by that statement, then you lost me on it.

A pencil is an amazingly simple tool, and so is a piece of paper. Yet to truly master those tools can be quite complex, and difficult for some people. In some ways, cameras can be all too simple, and quite easy to master. When the tools do not hinder your creativity, then you have mastered the tools.

"We run into problems when we want to reinforce our choices, or quantify our choices. We can define for ourselves a basket of criteria of needs, then slot an imaging system into those needs, and in that process identify our ideal imaging solution. When that does not hold up is when we try to apply that to others, . . ."

Gordon, I am working hard to understand this...... tell me if I got this right.... you are saying.... some of us, attempt to "reverse engineer" an imaging solution....then we try it, but it fails. This forces us to push the failure onto others.... do I have this right? For what reason would someone do this ?

That's an odd twist on what I stated, and I'm not sure how you managed that, or why.

There is a need amongst some to justify why you made the choices you made (you meaning all people, and not specifically you Mr. Click). Re-inforcement could come from convincing others you made the best choice, or at least a damn good choice. That is not right or wrong.

Suppose I wanted to take photos of dangerous animals in their environment. If I had a really long telephoto lens, it would be far easier than if I only had a wide angle lens. Though if I told someone that "this 6000mm Canikony lens is the best lens ever made", then that claim only works for my specific needs, regardless of data that might show how truly wonderful it performs.

Taken more simply, I have often heard people state how wonderful some particular DSLR or MFDB performed, sometimes even showing you data to prove how great it worked. Taken to an extreme, some people will look at you like a space alien simply for mentioning that you use anything other than the latest technology, as if technology in and of itself was so wonderful that you would need to be a fool (or a space alien) to even consider using something older. In fact, film users, no matter how young, can be often called Old School.

So who is right? Or is there even a need to be right? Why? Why not?

Just because I usually take a Shen-Hao 4x5 to a location for a paid advertising shoot, only use transparency films, and only deliver scanned files, does not mean I think everyone else should do what I do. I have found my ideal imaging solution. I would never suggest that someone else's choice was inferior, nor would I suggest that their choice was superior.

"Drawing and painting are hopelessly obsolete, low resolution, low tech, and at times downright cheap."

IMO, the EXACT opposite is true... Us LF photogs can ONLY dream of the day when a LF print garners the same respect as an oil painting of the same scene.... sad but true... the ratio of galleries in the USA, paintings vs. Photography is probably 500:1 or greater. This speaks volumes on the publics perception of "what is art" .....

Wow, you completely missed my point. How much does a pencil cost? How much is paper? Compared to transparency film and a 4x5 set-up, some oil paints are actually affordable for some people. While a do own several hundred dollars of brushes, painting could be done at a lower cost than large format colour imaging.

There can often be more effort that goes into hand made artwork, but there are also five minute paintings. Oil painting has a far longer history in the world of art, and it is less accessible to the masses to do it themselves. Compare that to many people thinking it is all too easy to pick up a camera.

Now if you take Gursky, Richard Prince, Burtynsky, or a handful of others into the mix, then photography can garner big dollar amounts. These are the exceptions. On a lesser known artist scale, those who paint or sculpt will often get more respect than photographers, and I don't have a problem with that, though that wasn't my original point.

Ciao!

Gordon Moat Photography (http://www.gordonmoat.com)

bglick

23-Jan-2009, 00:12

> BG, 10ft prints are not the average size for the average home. But other artists target the wealthy market (eg- Peter Lik with many 3 meter prints).

You are preaching the choir Van.... I have sold many prints 20 ft long... some prints hangin in my home are 11 ft, panoramics. Of course, not everyone shares my love of HUGE prints. Liks long prints are from 6x17.

> When you need that level of quality, large format film is the only choice.

I have some 10 ft stitched DSLR shots that are as nice as anything I have ever produced, which include Seitz 220VR and 4x10" captures. Lots of options today....

Thanks for the APUG link on some of films accolades. good info, although I was a bit dissapointed that Kodak will not release the new Ektar 100 in 8x10...bummer... Also the Fuji 6x7 folder, spring 09...encouraging. I hope they offer it in several fl's.

Its too bad there is not a new, low cost, ($5k ?) LF film scanner of high quality for sale today... maybe up to 8x10, with excellent lenses, high optical dpi and Dmax. Since a scanner is a digital device, I think it could be done... just like HD tv's in 1996 were $15k, now ones 4x better sell for $1500. Scanners will have surely benefitted from the continued advances in digital capture..

> They have a 65mp camera with capability of 50fps, and a 617 digital format (261mp-and 25fps) coming out ini 2010.

Did you see the price tags? Not sure this will sweep the world... high end market will love it.... but not the masses. Can't see a large dent in the market. Your other comments are well received.

While I do agree there is some who don't know how to use a computer, they are dying off. The new generation certainly does, and therefore, IMO, PhotoMerge will slowly make a dent into film, as stitching is such a powerful capture method, simple to merge in PS, no film, no processing, no scanning, scanning fluid fumes, etc. etc. Anyway, just my $.02.... I think we are safe for the near future, then, no one can predict.... AND, there is one big safe-guard if dooms day comes.... deep chest freezers.... film stores very well at 0 deg F! You can store enough to last our life time! So I don't fear the loss of film...

Don Hutton

23-Jan-2009, 05:42

The following comments by Henning Serger...."In the last two years Kodak introduced 11 (!) new or improved films: Portra 160 NC-2, 160 VC-2, 400 NC-2, 400 VC-2, Portra 800 version 3, improved Gold 200 and Gold 400, Portra 400 NC-3 and Portra 400 VC-3, TMY-2, Ektar 100.

I grew up in in the golden analogue days. But I can't remenber a time in the past, when Kodak introduced 11 Films in only two years. Please correct me if I am wrong.
Look back at summer 2006: Anyone here on apug who thougt that Kodak will bring 11 new films to the market in the next two years?http://www.apug.org/forums/forum172/54564-photokina-positive-news-film-4.html
Worth mentioning that, by your logic, they also discontinued 10 films in the past two years two (all the previous iterations of those films, except Ektar 100 which is actually a "new" film altogether).

They also completely discontinued Kodak HIE.

Like yourself though, I'm delighted that they still seem to be throwing money at developing their analogue product line even though I don't see 10 new choices on the shelf - really just the same (except Ektar 100....) with some minor improvements.

bglick

23-Jan-2009, 10:44

The fact ektar 100 will not be in sheets, says something about Kodaks position on LF film sales, right?

Eric Leppanen

23-Jan-2009, 12:02

The fact ektar 100 will not be in sheets, says something about Kodaks position on LF film sales, right?I wonder about this. I'm not so sure. When Ektar 100 was initially announced I was enthusiastic about it as a possible chrome replacement (I have historically carried both chrome and color neg) if it ever came out in LF sheet sizes. But the primary benefit of color neg film for me is exposure latitude (I use Portra or Pro 160S for high contrast scenes, and use every bit of that -2 to +3 stops of exposure latitude that those films offer), and I noticed that Ektar 100 offers only -1 to +2 stops. So for me, Ektar is a "tweener", occupying a market space between high latitude neg films and chrome. It cannot replace my existing color neg films, and if I'm therefore still stuck with carrying two film types I'd still prefer to carry "high latitude color neg" + chrome, as chrome gives me a wonderful positive image and enables cheaper processing (in my area, E-6 sheet processing is much cheaper and more readily available than C-41) and a much wider choice of digital print labs (many such labs do a fine job with chrome film, but few handle color neg properly).

My take is that Ektar is targeted at the consumer market where folks get their film processed at Costco or Walmart (consumer E-6 processing being long extinct), and want to save money (or avoid anything computer-like) by using that old beater 35mm camera in the closet rather than coughing up for a new digicam. Since LF shooters use pro labs, they do not fit this consumer business model. I have also heard speculation that Ektar was targeted at the Japanese market, where 35mm film retains a larger market share than in other countries, and Fuji does not offer a color saturated neg film.

So if Ektar came out in sheet sizes, I'm not sure many LF photographers would buy it. Perhaps concerns along these lines is holding Kodak back, rather than a lack of belief in the sheet film market (reportedly Kodak has internally tested Ektar in roll and sheet film versions). Then again, maybe I'm not typical... :)

Bruce Watson

23-Jan-2009, 14:57

The fact ektar 100 will not be in sheets, says something about Kodaks position on LF film sales, right?

Yes it does. To me it says something about how amazingly good 160 and 400 Portra are. The bar is set pretty damn high. From what I read about Ektar 100 so far, it would have a tough time jumping that high.

What Ektar 100 has I don't need or want. Finer grain than 160Portra is meaningless in 5x4 and larger. Really. And the last thing I want or need is "ultra vivid" color. I'm not after clown colors, I want something more real. So yes, I'm using the NC versions of the Portra films.

I think Kodak knows exactly what we LFers want. What Kodak has done for me lately is TMY-2, and the new versions of 160Portra and 400Portra. What more could an LFer want? Holy cats -- life is good! Thank you Kodak!

Eric Leppanen

23-Jan-2009, 18:48

Back to the original topic of this thread...the new crop of 20+ MP DSLR's may finally be prompting the long predicted MF digital price collapse. Take a look at a couple posts from the diglloyd blog, where he concludes that the new Nikon D3x is producing low ISO dynamic range and shadow detail that rivals some MF digital backs:

http://www.diglloyd.com/diglloyd/free/PushingTheBlacks/index.html

In the same blog entry he also notes a new Phase One promotion:

Looks like the increase in DSLR quality and the economy are leading to some extremely aggressive deals in the medium format world...

The latest promotion from PhaseOne: buy a P45+ digital back, and get the camera (Mamiya 645 AFD III) and five lenses which sell (street price) for about US$20,000. There is also a three-lens deal on the P30+.

Note that Phase is doing everything they can to avoid devaluing their franchise digital backs (giving away cameras and lenses instead), but if this trend continues digital back price reductions can't be far behind. The rest of the blog is here: http://www.diglloyd.com/diglloyd/blog.html

If this info was coming from just one Nikon enthusiast then I would be skeptical, but I'm getting similar vibes from a variety of sources.

I certainly would hold off making any major MF digital back investments until the smoke clears...

Bruce Watson

23-Jan-2009, 20:04

bglick

23-Jan-2009, 23:47

Nice response Bruce....

I updated my graphic for final print sizes for 5 formats at different DOF scenarios, in a new thread...

http://www.largeformatphotography.info/forum/showthread.php?t=45186

Frank Doering

24-Jan-2009, 11:59

I love crunching numbers. But for real world comparisons, there is occasionally a point to pixel-peeping. Here is a real life comparison from two architectural shoots, 4x5" film and Nikon D3, both off a sturdy tripod, with mirror-lockup for the Nikon. I don't remember exact sharpening routines, but for the observed differences they don't matter.
http://doeringphoto.com/temp/testimage_small.jpg
100% crops at http://doeringphoto.com/temp/testimage.jpg

rvhalejr

24-Jan-2009, 14:31

...but for the observed differences they don't matter...
100% crops at http://doeringphoto.com/temp/testimage.jpg

I'd like to read the small print on the clock. If your in the mood see if you can
resolve it in the image plane (with the help of a 40x loupe) and if so maybe try
to get it on ISO 25 film .,.

You got guts using a 24mm on the DSLR to approximate the 4x5 90mm .,.

Frank Doering

24-Jan-2009, 15:42

rvhalejr, maybe I wasn't clear: the differences are obvious: the 4x5" negative smokes the DSLR at the 24x30" print size. I didn't try to approximate, I just needed a color image for a small repro size.

Reading the fine print: the small letters on the clock face are about 0.05mm tall on the negative. Making them legible would require, I imagine, at the very least 4 cleanish line-pairs per letter height, i.e. around 100 lp/mm. Good luck at f/22 which I needed for DoF. At any rate, in order to read the letters in the 24x30" print you'd need tremendous eyesight because the lines are 1/3mm tall.)

Kirk Gittings

24-Jan-2009, 18:18

Frank, the outcome of your comparison seems quite obvious from the get go. I'm not sure what the point was really. Actually I guess, it was not set up as a test was it? Just a defacto comparison because you happened to shoot both on a job. To be fair the best test would be the current top rated DSLR, the Nikon D3X with a first rate prime lens against a drum scanned 4x5. What would be more enlightening even still would be to see how many stitched images it would take with the D3X and a primo prime lens to equal the 4x5 in resolution, 2X, 4X, 8X, 16X including a test for DR? If I had access to the Nikon equipment, I would love to try it but I don't unfortunately.

Gordon Moat

24-Jan-2009, 18:28

One thing I thought of with Frank's two images was exposure. In the case of 4x5, with a small enough aperture and long exposure, a swimmer in that should would appear as a blur, unless the swimmer was lit with a strobe. Compare that to stitching, and again there would be some trouble having a swimmer in the shot.

Ciao!

Gordon Moat Photography (http://www.gordonmoat.com)

rvhalejr

25-Jan-2009, 16:18

rvhalejr, maybe I wasn't clear: the differences are obvious: the 4x5" negative smokes the DSLR at the 24x30" print size. I didn't try to approximate, I just needed a color image for a small repro size.

Amen, No disrespect intended or implied.,. :p I simply LOVE real world comparisons and yours is great !!!

Reading the fine print: the small letters on the clock face are about 0.05mm tall on the negative. Making them legible would require, I imagine, at the very least 4 cleanish line-pairs per letter height, i.e. around 100 lp/mm. Good luck at f/22 which I needed for DoF. At any rate, in order to read the letters in the 24x30" print you'd need tremendous eyesight because the lines are 1/3mm tall.)

Absolutely Outstanding Example and well proven procedure.

I digress as the (arguably loopy) 35x-40x Loupe researcher (and a fanatical film flatness person) attempting to push the envelope in small way, maybe from 3200dpi (commonly practiced) to 4000dpi (a rarity with good reason).

Using this as a textbook example (with the final product being High IQ pixels ref
...largeformatphotography.info/forum/showthread.php?p=430929#post430929
...largeformatphotography.info/forum/showthread.php?p=431786#post431786
resulting from an arguably fairly consistent yield) I'd like to know if some bracket shots (with the following criteria) might be capable of resolving the small clock letters (lets stipulate in this example the clock OEM is interested in your piece).

I've included four images that suggest if the lens is outstanding (a given) and a 40x loupe used to dial in the peak Point-of-focus behind ideally perfect ground glass (intentionally staying away from plenums here), with a finely calibrated system (another given) and ISO 25 film flat to within .001" AND a tilt angle of not more than 1.5 degrees (I'm admittedly a newb at the very subtle art of tilting).

So the DOF calculator image seems to indicate 17ft at f22, but perhaps f16 or f11 might work if I'm interrupting the tilt spreadsheet correctly.

The defocus spreadsheet images attached seem to suggest that a very slight defocus might be acceptable and perhaps allow one (in theory) to approach 100 lp/mm resolution (under ultra precise conditions and restricted criteria).

In this model (admittedly not yet verified and poorly integrated) film flatness to .033mm (as an approximation to .001") would be critical since there would is only a tiny amount of defocus allowable (all sources summed) without diminishing the resolution (or bending of straight lines).

DISCLAIMER
I've indicated that these images are of a --DRAFT-- nature as the likely hood of a significant mis-understanding is fairly significant. I do admire your posting the film and DSLR together (I think everyone uses both) because on occasion I've felt the need to use "I'm putting on Body Armour" now or the "Here sharky, Here sharky-Sharky" to try and lighten things up a bit. ;)

I'f anyone sees any glaring mistakes or assumptions please comment.

Frank Doering

26-Jan-2009, 09:01

Kirk, you are right, I didn't set up a test. The point of posting the images was to inject some visual evidence into a thread discussing the resolution limits of LF film as against various digital options. Eyeballing my images, I find them in good agreement with the calculated numbers bandied about here: it would take a file at least four times as large and of the same quality as the 12MP D3 file to get into the ballpark of the (down-sampled) 4x5" scan. I also wanted to offer a visual comparison to those who don't have access to both kinds of system. I suspect that there are many LF shooters on the fence who wonder which jobs can be done digitally with a system that can be amortized in a small business.

Incidentally, I sure hope Nikon primes do better along the edges than this allegedly superb zoom. Being used to LF lenses, I have found the lenses for 35-mm digital to be disappointing. Poor edge performance aside, they all distort significantly, which means you lose detail in the correction. The posted D3 file shows this loss. This is another reason for doing real-world comparisons: if you care about straight lines, your final 35-mm digital file will never quite preserve the detail of your RAW files. As for DR, film still wins in my books. Shooting architectural interiors, for example, I always find myself layering different digital exposures where one sheet of film would capture the brightness range.

Gordon, your point about blur is well taken. It cuts both ways: if you want blur with digital, you'll sometimes need a ND filter in order to get sufficiently long exposure times. I haven't had much luck with stitching because there always occurs some important change during the exposure series that I can't rectify later: the light, the wind, people, cars... One-shot capture is also much easier to compose.

rvhalejr, it would be fun to tinker along the lines you suggest. But it wouldn't be very practical in the real world of impatient bathers waiting to get into the pool. I have never managed to set calculated tilt angles even remotely precisely enough, nor have I been able to estimate Merklinger's parameters. In real life, I start out zeroing the standards with a mirror device and then adjust by ground-glass inspection with a 7x loupe. Doing that off-center opens another can of worms: the tricks played by the Frensnel lens, light falloff...

bglick

26-Jan-2009, 13:51

> I start out zeroing the standards with a mirror device and then adjust by ground-glass inspection with a 7x loupe. Doing that off-center opens another can of worms: the tricks played by the Frensnel lens, light falloff...

Nice post... This is just one of MANY reasons why there is limits in how accurate you can try to focus or align anything with view cameras.

In addition, a 40x loupe on a gg which is only capable of ~ 3 lp/mm resolution, is well..... not providing any added useful information. This is why viewer camera makers sell gg loupes in the 3 - 6x range, as more magnification serves no purpose.....if it did, they would offer us 7 - 40x loupes as well.

rvhalejr

26-Jan-2009, 15:27

... behind ideally perfect ground glass (intentionally staying away from plenums here) ...

Loupe Stands and Plenum (in place of GG when focusing with 35-40x Loupe)
...largeformatphotography.info/forum/showthread.php?p=423824#post423824

rvhalejr

26-Jan-2009, 16:55

Loupe Stands and Plenum (in place of GG when focusing with 35-40x Loupe)
...largeformatphotography.info/forum/showthread.php?p=423824#post423824

DISCLAIMER: I'm not getting paid by View Camera, Film or Digital Back OEMs to write this stuff nor do I have any financial interest or feel any need to favor one perspective over another.

DATA POINT ON FILM SCAN MP yield VERSES END PRODUCT yield.

22-Jan-2009, 21:31
...largeformatphotography.info/forum/showthread.php?p=432705#post432705

...
SNR Noise Reference ...imatest.com/docs/noise.html (Standard Deviation)

The Following Approximates End Product YIELDS for various formats
(DeFocus <= 0 mm; film flatness <= .001 for LF)

Let SNR for 4x5 film = 1/3 (200MP film scan yields about 65MP);
1.75 MP per cm^2 from 3200dpi fluid film scan (10cm x 12.5cm == 125cm^2)
0.58 MP per cm^2 end product yield

24-Jan-2009, 18:59
...largeformatphotography.info/forum/showthread.php?p=433165#post433165

Image Annotation 100ASA 4x5 90mm scanned 3200dpi downsampled to 7200x9000

So both posts seem to be using similar numbers (7200x9000 == 65MP and 4x5x3200x3200 == 200MP) for film scan pixels and end product yield which after all this time should not be that much of a surprise.

Another WONDERFUL attribute of Frank's example is that it has two of the three principle photographic reference B&W and E6 (similar to the digital look) is shown.

The third fundamental type is portraiture that originates from one and only one type of film and unique glass that yields images that appear to glow (a property of diffusion). The third type cannot/should not/will not be characterized by any cy/mm in any meaningful way.

IMO portraiture has been (and will continue to be) Top-end digital's greatest challenge. There may be an analogy here between the overly sharp look of video as opposed to scenes shot with c41 like film.

I've seen (or heard of) solutions for great resolution and ever improving dynamic range of digital technology. I have yet to see anything approaching what PortraNC can achieve behind the SA 65mm with a Polarizer (or Graduated NDs), UV, Skylight or appropriate mired filter given the color temperature on any given day at any given time of year.

Anyway, Frank's example of shooting a pool with different cameras is a great idea.