Scanning 11x14 BW Negatives

[rawitz]

I'm not disagreeing with you. What I;m saying is that because enlargement is less on the 8x10, optical diffraction will not be seen. The picture will look just as sharp as the 4x5 that used a larger aperture. No? Yes?

Yes and no. Your argument that for the same(!) final enlarged printsize every physical differences described here in DOF, resolution and diffraction (and film) will be equalilized, I myself cant calculate it mathematically, but in practice its the simple truth, the larger the filmformat following all technical rules as said here the better the result for the "possible largest analog or digital print" is. What you want as "largest" print is your personal decision not physical determined.

[Alan Klein]

Alan, check some diffraction charts and take a look at max resolution for given apertures. Then consider enlargement ratios and calculate it.

Of course all the math says is hypothetical but it's a baseline. Personally when I tried to get max resolution with the largest aperture possible for a needed DOF I was always disappointed and decided it was better to have slight diffraction than slight out of focus. Ymmv.

When I started shooting medium format landscapes 35 years ago, I would calculate the aperture I would need for the DOF I wanted in a particular scene. Then I would stop down one extra stop for good measure. I never thought about diffraction, right or wrong.

[Joseph Kashi]

sorry to ask this question everyone seems to be dancing around, but how large are you planning to make your prints? you really don't need to have gigantic scans to make big gargantuan prints ...
might be easier to curtail your scanning to fit your end image size. that is unless you are commissioned by your gallery because they already have buyers for your giant artworks.

It's possible that there's a larger than 24" wide printer in my future and I have a great deal of RAID hard disk space. So, there's no practical reason to limit my scans to only fit my current 24" digital printer, if not some third party's wider format printer. It's worth having higher resolution scans just in case I need to print larger than 24" wide at some future time and have the capability to do so.

[rawitz]

Thats right. If you want to shoot the same (reality) picture with 4x5 or 8x10 format with the same (!) DOF , you have to double the lens focal (150mm to 300mm) and then you have to double (numerical) the f-stop. Practicaly spoken: a 4x5 film with lens 150mm and f-11 is the same in picture view and DOF (! thats the argument of corran) as in 8x10 film with 300mm lens and f-22, everything else in technic and optic being perfect. Only the resolution doubles, so you can make 4xsize prints with 2xresolution.

This is valid for best sharpness and equal DOF on film!.
But in the conventional photografie DOF is defined and calculated for the (same) print-size!
For a 10x enlargment of a 4x5 you only have to enlarge a 8x10 5x, so for school photografie the 8x10 DOF tolerable unsharpness-circle doubles. The common DOF calculators set by convention (not by physic) an unsharp circle of 0,1mm as tolerable DOF limit for 4x5, for 8x10 its 0,2mm and for 11x14 is 0,3mm.
In my practical example above now a picture of 150mm lens and f-11 will be the same in DOF as a 300mm lens and f-11, because we only have to enlarge the 8x10 half.

But I for my LF photografie dont follow this rule. The DOF defined unsharp-circle for 4x5 is 0,1mm =5 lp/mm, for 8x10 is 0,2mm =3 lp/mm and 2lp/mm for 11x14 and so on. My limits are much more critical.
With modern film, modern lenses and modern scan technic I but can extract about 50 lp/mm from any filmformat.
So I better double the DOF calculaters f-stop, for example from f-11 to f-22.
But its your personal choice, if you make contact-prints and max. print sizes of 12x16, your personal DOF is much more tolerable than the conventional DOF, the opposite what I do and your are right too.

For the discussion here: DOF tolerable unsharp circle is not diffraction unsharp-circle!

regards
Rainer

[Alan Klein]

This is valid for best sharpness and equal DOF on film!.
But in the conventional photografie DOF is defined and calculated for the (same) print-size!
For a 10x enlargment of a 4x5 you only have to enlarge a 8x10 5x, so for school photografie the 8x10 DOF tolerable unsharpness-circle doubles. The common DOF calculators set by convention (not by physic) an unsharp circle of 0,1mm as tolerable DOF limit for 4x5, for 8x10 its 0,2mm and for 11x14 is 0,3mm.
In my practical example above now a picture of 150mm lens and f-11 will be the same in DOF as a 300mm lens and f-11, because we only have to enlarge the 8x10 half.

But I for my LF photografie dont follow this rule. The DOF defined unsharp-circle for 4x5 is 0,1mm =5 lp/mm, for 8x10 is 0,2mm =3 lp/mm and 2lp/mm for 11x14 and so on. My limits are much more critical.
With modern film, modern lenses and modern scan technic I but can extract about 50 lp/mm from any filmformat.
So I better double the DOF calculaters f-stop, for example from f-11 to f-22.
But its your personal choice, if you make contact-prints and max. print sizes of 12x16, your personal DOF is much more tolerable than the conventional DOF, the opposite what I do and your are right too.

For the discussion here: DOF tolerable unsharp circle is not diffraction unsharp-circle!

regards
Rainer

What does that mean? (For the discussion here: DOF tolerable unsharp circle is not diffraction unsharp-circle)

[rawitz]

What does that mean? (For the discussion here: DOF tolerable unsharp circle is not diffraction unsharp-circle)

In short: DOF sharpness increases by aperture stopping down. And lens sharpness increases by lens aberration minimizes. But opposite the physic diffraction of light at the aperture borders decreases overall sharpness by stopping down aperture. The f-stop, where lens sharpness gain and diffraction sharpness loss are equivalent, is called the "critical aperture".

For analog film-photography (20lp/mm) the math calculation give the critical f-stop 22, no matter what film format or lens is used. This is why lens brands publish there MTV lens-specs for f-22 as optimal aperture.

But for best DOF you sometimes/often stop down to more than f-22. The larger the filmformat (4x5 to 8x10) the more you have to stop down for equal DOF (f-22 to f-45). This is the argument of Corran against ULF 11x14 above.

But the second step is: how much diffraction is tolerable by stopping down for DOF before is gets visible on film in general unsharpness?
The school-photography calls this the "beneficial aperture". And while the "critical aperture" is physic, the "beneficial aperture" is convention based on photographic experience.

For LF-film-photography the recommended "beneficial aperture" is f-32 to f-64 relative to filmformat. If you calculate the "beneficial aperture" with the "conventional DOF values" its even much smaller.

regards
Rainer

[Tin Can]

How Many Megapixels Do You Need to Print a Billboard?

https://fstoppers.com/originals/how-...llboard-220239

Not FOV or Depth of field

Viewing distance

[Corran]

Alan - consider this:

4x5 film
96mm x 120mm
Theoretical diffraction limit at f/22 is 70 lp/mm
This would be 8400 lp on the long side
5-6 lp/mm is considered good print definition at normal viewing distances. Let's choose 6.
8400 / 6 gives max print size, so 1400mm = 55 inches on the long side

Now consider 8x10
200mm x 250mm
Theoretical diffraction limit at f/45 is 35 lp/mm
This would be 8750 lp on the long side
Again, 5-6 lp/mm is good print definition. Let's choose 6.
8750 / 6 gives max print size, so 1458mm = 57 inches on the long side

This is just the math that I was referring to. You can extrapolate this to any format and find similar results, but what you'll find is once you go to 35mm you are talking about apertures of f/4 and the need to put 400 lp/mm down on the film to get "equivalent resolution." But that isn't going to happen, either due to lens limits or film limits. Within this framework 4x5 seems to be at a real sweet-spot in terms of actual results, with larger formats quickly becoming a diminishing return, and that was my original point. Others obviously may disagree. However I would also point out that one quirk here is scanning - 4x5 scans on typical flatbeds can only get so much information due to the limitations of the scanner, about 70% at best from my estimate based on Epson's roughly 2200 DPI rating that others have tested. Once you get up to 5x7 and larger the scanner is no longer the limiting factor, so to be fair there will be a modest improvement just from that.

Ultimately just do whatever you want, this is all mostly irrelevant in actual practice. I do like numbers though.

[nolindan]

Viewing distance

Properly, pixels per degree of arc, which does correlate with viewing distance but may be easier to deal with for calculations.

Google sez ~0.5 arc-minutes/0.008 degrees is the limit of a young healthy eye of distant memory. So, one pixel per 0.008 degrees would seem a reasonable criteria.

Simple trig leads to:

PPI = 1 / (viewing distance in inches * 0.00014)

Where 0.00014 is the tan of 0.008 degrees - at small angles sin = tan = "close enough for government work."

Something 30 inches away would need 240 pixels/inch

A billboard 50ft / 600" away would only need 12 pixels/inch

But that is for well delineated square pixels - which most printed pixels aren't.

[Sal Santamaura]

...I never get the whole sharpness resolution stuff that a lot of people who love to use LF (or any kind of camera/lens system) get zero'ed in on.
reality isn't sharp, and there isn't extreme DOF...

On the contrary, assuming a fully functioning human eye-brain system, extreme depth of field with everything sharp perfectly replicates reality. Our eyes scan what's before us and focus ("accommodate") to every part of the scene at all distances. We continuously move our gaze to elements of interest and the center of our eye renders them in sharp detail. The only way a photograph can simulate reality is to ensure that, regardless of what part of it we look closely at, it's in focus and detailed.

Of course, those with uncorrected vision defects might have an alternative concept of "reality." Whether optical or other aspects of perception.