DIY DSLR Scanner vs Drum Scanner

[JasonF]

Hello,

I really love the idea of the DSLR scanner. But, I'm really struggling with something ...

Film Grain and Aliasing:

http://www.photoscientia.co.uk/Grain.htm

The above link pretty much sums up the issues I am having with my own DSLR scanner. Thus, the idea of using a DSLR scanner sounds great at first. But, this method seems to suffer from the problem of scanner aliasing. And to be honest, I'm not sure what to do about it. And, I'm also still trying to understand it...so bare with me.

From that perspective, I can see the attraction to drum scans for the best of scans. However, my hope, was that a DSLR scanner could at the very least match a drum scanner if not surpass it. Why? Drum scanners are highly expensive (easily a few thousands dollars), bulky, have fewer companies producing them today then in years past, and all around not cost effective for the average Joe. Not all film merits that of being drummed scanned, but when I do, I'd like to be able to have them done in a feasible way. And this is where, I thought, the DSLR scanner would come in and help the average person out. For me, I already have a DSLR and lenses....and that's why I'm testing the waters with it.

What makes the drum scanner most effective over that of a flat bad scanner, DSLR scanner, or otherwise is the PMT and the ability to control the aperture. This is discussed here:

http://www.karimsahai.com/2010/08/sc...-drum-scanner/

Drum scanners fulfill the same role as any other film scanning device, while relying on an entirely different technology: photomultipliers, or PMTs. In essence, PMTs are extremely sensitive particle detectors tuned to respond to uv, infrared and visible light (photons). The principles at the heart of a drum scanner were derived from research in the field of nuclear physics, in which scientists observe and measure the results and effects of particle collisions. In the case of drum scanners, several photomultipliers are combined to offer the very best scanning device for photographic film. PMTs act as photon collectors and bypass the methodology used in CCD scanners which is to amplify an electrical current. Drum scanners do not suffer from the CCD side-effects that we know: noise & limited dynamic range, specially in shadow areas of your film. The ability for drum scanners to vary their built-in aperture to match the grain size of the film you’re scanning; their ability to scan all film formats including very large exotic sizes and their ability to offer superior batch scanning capability (you can fit a LOT of images on a single drum. Some drum scanners are sold with multiple drums) make them the very best scanner there exists for quality-conscious photographers who want to capture all the range that is encapsulated in their film, at very high resolution.

This ability of the drum scanner to adjust the aperture to match that of film grain seems to be the overriding advantage that it would have over flat bed scanners, DSLR scanners, or otherwise.

My question out there who may know this better than I, is if there is a way for DSLR scanners to overcome the problem of scanner film grain aliasing that drum scanners seem to have the ability to overcome? Using a DSLR scanner, is there any techniques that can be employed that would help to minimize the scanner aliasing issue and therefore pull out more of the picture/image from the film?

Wiki has a section on this called "Grain effect with film and digital":

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

In there are two images:

http://en.wikipedia.org/wiki/File:Ma...Norway1991.jpg
http://en.wikipedia.org/wiki/File:Ma...y1991Grain.jpg

The zoomed in detailed one is pretty much the result of what 'I see' in my own images scanning with the DSLR scanner. You get what looks like colorful noise in the image with a lot of grain. Again, this is what I also see and suffer from.

Apparently, if a drum scanner were used, it would be able to pull out more of the image from the picture than the grain. But, I have yet to see some comparisons of this.

For example, controlling the aperture on a drum scanner to match the film grain, what would the resulting image look like over that of a slide/negative scanned by a flat bad or a DSLR scanner?

Anyway, this is what I am struggling with: how to overcome the scanner aliasing issue that drum scanners seem to have over DSLR scanners? Or, if there are any techniques that DSRL scanner users can apply to effectively match the same quality that a drum scanner can perform? Or, for all I know, DSLR scanners by their very nature just can't compete with the drum scanner regardless of how many megapixels the DSLR scanner has? For example, can I conclude that even a Hasalblad H5D-60 with a 60 Mpixels (8956 x 6708) sensor and a good lens could not pull out as much detail from film than that of a drum scanner due to scanner aliasing issues?

Here's a blog that touts the ability of the DSLR scanner:

http://jamiemphoto.com/blog/2013/12/...t-film-scanner

The title is, ""Yes, Your DSLR Really Is the Best Film Scanner". Hmm, but is a DSLR really the best film scanner? I'm not entirely sure if DSLR scanners suffer from scanner aliasing issues as that is what I have run into as my problem with DSLR scanning approach. Or, maybe the author of this article is applying techniques that are well know by others to overcome this but that I am not aware of. If so, I'd love to hear what those techniques are.

Thoughts?

[Noah A]

I've never tried the dslr scanning method, but I followed the last link in your post, and the author is using a central square to shoot Hasselblad 6x6cm negs with a nikon DSLR, resulting in a 12-16mp image. I can tell you with certainty that drum scanning a Hasselblad 6x6 neg will give you a much higher resolution. It's unclear from the post if the author has ever actually tried a drum scan. He does mention a Nikon Coolscan. I used to scan on a Coolscan and my medium format scans on that machine were also much better than 16mp. The author seems more interested in speed and convenience than in ultimate image quality. That's fine, of course, but since you're concerned about grain aliasing it sounds like you may be more interested in image quality.

Of course folks who are really trying to maximize the quality of dslr scanning are probably stitching multiple frames, but then of course the dslr scanning process won't be quite as fast or convenient. There are some detailed posts on DSLR scanning on this forum somewhere, so you should search them out if you haven't already done so.

The drum scanner has a few real advantages. First, the fact that the film is mounted to a drum ensures proper focus across the frame. Second, the mounting fluid helps fill in small scratches on the film, making them mostly invisible in the scan. Most importantly, as you mentioned, the scanner's aperture adjustment can be used to change the look of the film's grain. It's possible to use a smaller aperture to get extremely sharp results that emphasize grain, or a larger aperture to really minimize the grain. I choose an aperture somewhere in the middle, and the results look very much like the grain I'd get from an analog print.

I'm extremely happy with the results I get from my Howtek HR8000, but again I've never tried dslr scanning so I can't really comment on the comparison. I wouldn't say that drum scanning is difficult, but there is a learning curve to be sure, and it's a skill that could take some time to master. It also can be expensive and time-consuming. But if you're really after the ultimate image quality, it's a proven technology that produces incredible results.

I use an Epson V750 to do preview scans and the drum scanner for my final scans. Depending on how much you shoot (and how many final scans you need to make), it may make sense to do preview scans yourself on a flatbed then outsource the drum scans.

[mdarnton]

I use a camera for scanning. Mine is a 12Mp D300, with micro-Nikkor. For 35mm it's great, much better than a flatbed. At 6x6, it's just a hair behind the scanner because the camera's image is less smeary than the scanner's slightly higher res smeary version), and with the writer's D600, the camera is still probably better than the scanner. For anything larger, the flatbed wins, for my D300. I don't know where the crossover point would be for a D610, or better yet, a D810--somewhere around 4x5, probably. I haven't had any reason to use a drum scanner, but sure, a drum scanner should beat any of the above. Lots of people use flatbeds, but they are not all that great, just cheaper than a drum. However, I rarely make prints larger than 8x10 or the next size up, where I doubt there'd be a gain.

The grain aliasing problem depends a lot on exact grain size vs scanning dot size. It's more of an interference pattern than anything, and so it's dependent on several things. If a flatbed were sharp enough, it would probably have the same problem, but flatbeds just aren't that sharp compared with a camera in a 1:1 faceoff. The reason the scanner wins on larger sizes is simply that my D300 is limited to 2800x4200 pixels, no matter what it's scanning. A scanner, which tops out (actually) around a smeary-looking 2200ppi can't beat my camera on a one inch scan (2200 vs 2800) but it can certainly beat it scanning 4x5 at 2200 per INCH (yielding 8800 total pixels per width on the 5" width) when my camera is limited to 2800 TOTAL, regardless of the width of the neg.

What you do depends on what you need, right? I'm never going to make a 30x40 print, probably. . . .

[Peter De Smidt]

What camera and lens are you using?

Aliasing, an interference problem, can be minimized by increasing the resolution of your scan. With stitching and focus stacking, you can get as much resolution as you'd like. I use a Rodagon D 75mm F4 at 1x for all of my scans, regardless of the format. (At 1x I don't bother with focus stacking. The film is wet-mounted to a very flat plate of glass.) With BW film, even Technical Pan, I found moving up to 2 to 3 times was not worth the effort. I don't have very much experience scanning color with the Dslr scanner, though.

With my Cezanne, a pro flatbed, scanning at 6000 spi gives the best rendition of 35mm grain, i.e. the grain is the smallest and most even it can be. Lower resolutions scans gave noticeably coarser results.

Regarding http://jamiemphoto.com/blog/2013/12/...t-film-scanner, I would be wary of any article that claims that a given technique/system is the "best" without presenting very carefully done comparisons.

[JasonF]

Hello Peter,

Thanks for your input on this. Believe me, I would love to make this work.

What camera and lens are you using?

Currently, I have a bellows setup with my Canon DSLR and a Canon EF 50MM 1:1.8 lens. At first, keep things simple right and start with what I already have an own. With this lens, I am able to get some good magnification. The biggest question, is how much magnification am I getting? This I am not sure yet. And, how do I know when I am pulling too much magnification out of the lens before perhaps the lens isn't resolving as sharply anymore? Not sure just yet about that question either. I might have to do some lens calculations to better understand what magnification I am getting. But that should answer your question as to what type of lens I am using.

I'm of the understand that a lower MM lens will pull a beter magnification then that of greater MM lens. I see you are using a 75MM lens. Wouldn't that just give you more of a working distance? For film, it doesn't hurt to be close to the film. But, I need to first understand the pro's and con's there too.

Aliasing, an interference problem, can be minimized by increasing the resolution of your scan. With stitching and focus stacking, you can get as much resolution as you'd like. I use a Rodagon D 75mm F4 at 1x for all of my scans, regardless of the format. (At 1x I don't bother with focus stacking. The film is wet-mounted to a very flat plate of glass.) With BW film, even Technical Pan, I found moving up to 2 to 3 times was not worth the effort. I don't have very much experience scanning color with the Dslr scanner, though.

Great suggestions Peter. Do you have a collection of scans posted anywhere on the net of this scan-stich technique? Right now, I have only begun to explore the possibilities of DSLR scanning, but I have spent some time first doing some reading to see how others have been approaching this issue before attempting this path. But, I have not been satisfied as to what those techniques are to improve and reduce film grain ailising. And, also, because I seem to suffer from seeing it highly in my DSLR scans.

For me, my interest is in blank and white film, positive color slides, and negatives. And among these, I have various formats from 35mm and smaller to large format film.

For film, I am very much interested in stitching, but don't see much use for focus stacking considering that film lies along a plane. In this case, that simplifies things to where at the very least I can take focus stacking out of the picture.

You said that you found moving up to 2 to 3 times was not worth the effort? When you say 2 to 3 times are you talking about a 2x or 3x magnification?

You also made another good point that increasing the resolution of the scan would help better deal with the aliasing issue. Here's what John Striver said over at http://photo.net/film-and-processing-forum/00VDBX

The reason to use higher resolution in scanning is so that the lens serves as the required optical low pass filter. The grain on Ektar 100 may be so fine it's not a risk of grain aliasing. The risk comes when the grain is about the same "dot pitch" as the scan is at, that's when you get the "beats" that cause grain aliasing.

I've read this before that higher magnification would help which you mention here too. Recently spoke with a friend. He has a better lens that should be able to achieve a higher magnification. But, I'm not entirely convinced yet that would help much. But, I will borrow and pick it up and give it a try.

I've also read that it's better to scan at a higher resolution and then down-sample by about 50% to sharpen up the image. I will try these two approaches here shortly.

With my Cezanne, a pro flatbed, scanning at 6000 spi gives the best rendition of 35mm grain, i.e. the grain is the smallest and most even it can be. Lower resolutions scans gave noticeably coarser results.

So what are your thoughts on a higher magnification and then stitching since also having used a Cezanne? I'd like to try 1x, 5x, and 10x if possible and see if higher magnification and then down-sampling would help much? Perhaps you have a better perspective on this or may have already tried?

Regarding http://jamiemphoto.com/blog/2013/12/...t-film-scanner, I would be wary of any article that claims that a given technique/system is the "best" without presenting very carefully done comparisons.

I am wary yes. It's like "Hey trust me, use a DSLR. But I won't show you any of my techniques as to how I am pulling high quality scans using a DSLR". And, from my initial tests, I'm excited but at the same time a bit disappointed. I find hope in scanning and stitching, but in my scan test I suffer from film grain aliasing.

But all talk and no photo's make it less fun right? I'll have to try to get some captures together of my aliasing issues and post them on here. Then you can see for yourself what I suffer with. Then, I can try a few different lenses too to see if that helps to resolve the film grain aliasing issue.

[Peter De Smidt]

The easiest way to find out your magnification is to photograph a mm ruler parallel to the long dimension of your sensor. Compare that to your sensor size. In my case, that's 35.9 x 24mm. So when I have 35.9 mm when the image is sharply focused, then I'm at 1x magnification. I use the APO Rodagon D75mm F4, as it's the best lens for 1x magnification that I can afford. (http://www.bhphotovideo.com/c/produc...Rodagon_D.html). It was specifically designed as a slide duplication lens at 1x. (There's also an f4.5 version, which is optimized for 1/2x forward and 2x reversed.) The only lenses that are obviously better that I know of are the rare Printing Nikkors, and they cost thousands of dollars.

It'll be interesting to see what magnification your lens is at. It's a standard lens, right? Non-macro? If so, are you using it reversed?

Since you have Canon, check out Charles Krebs EFSC article at: http://www.krebsmicro.com/Canon_EFSC/

Regarding higher resolution and stitching, I stitch all of my medium and LF dslr film scans. Focus Stacking would add a lot of complication to the setup for large films. It would require another stepper axis on my machine, increased programming complexity for the robotics, and more complicated post processing. As I said earlier, with my system, I didn't see much, if any, advantage going higher than 1x, but that's with a very high quality lens at f4. At 1x, the depth of field of the lens is about 6 thousandths of an inch at f4. As you go up in magnification, that gets smaller. Down-sampling would help quality at the cost of a smaller file. I may go higher than 1x with 35mm in the future, but only if I can see a real increase in quality. I bet that people regularly overestimate the resolution of their film images.

[SergeiR]

Something to think about. IMHO.

- your dSLR will at best be 1/3-1/4th or mp it claims (unless you got Fuji, or true achromatic camera but its other kettle of fish) with infamous RGGB pattern of sensors. so you got whopping 4mp worth of resolution out of 12.
- even if you will get 12mp, its barely 3000x4000px. if you scan film @2400 dpi on flatbed it equals tooooo… right. barely over 1inch to barely under 2 inch scanning area. Considering that downsampling is possible we can say that you will have to go 4-8 times down on each side (4x5 film , 8x10 film judged). And we do talking true RGB pattern sensor btw (i.e array resolves single pixel for all 3 color values, not 4 pixels as in dSLR). Doesn't matter how smudgy - they still will be better. Tonal gradations still will not resolve fully in dSLR (12/14bit vs 24-48 bit will still loose).

film flatness, lighting, reflections, actually good micro-lens (which, by the way will detiorate quality at f16+ on your typical 35mm and sub - dSLR ).

If you can afford drum - get drum. If you can't - short of speed (but then if you going to do sliding back shots and glue panoramic results aka stitching - won't be much faster), even flatbed wins.

[Peter De Smidt]

My experience differs from Sergei's, at least with BW film. I get significantly better scans with a dslr than with an Epson flatbed, both in resolution and dynamic range. (I measured about 1000 dpi more resolution and at least 1 stop more dynamic range.) Comparisons, including those with an Edmund Scientific high resolution chrome on glass target, were posted in the dslr scanner thread years ago now. Some of the files aren't up anymore, alas. This winter I hope to have more time to do some tinkering and comparisons, but for the moment I don't have the time.

Btw. a good comparison of top scanners, by someone who owns and uses them, is message #42 at: http://www.largeformatphotography.in...-Scanner/page5

[SergeiR]

My experience differs from Sergei's, at least with BW film. I get significantly better scans with a dslr than with an Epson flatbed, both in resolution and dynamic range. (I measured about 1000 dpi more resolution and at least 1 stop more dynamic range.) Comparisons, including those with an Edmund Scientific high resolution chrome on glass target, were posted in the dslr scanner thread years ago now. Some of the files aren't up anymore, alas. This winter I hope to have more time to do some tinkering and comparisons, but for the moment I don't have the time.

Btw. a good comparison of top scanners, by someone who owns and uses them, is message #42 at: http://www.largeformatphotography.in...-Scanner/page5

Could be just b/c i am far less industrious than you I never attempted to build fully devoted station and stuff for such scanning.

[onnect17]

I would say the resolution of any CCD based system should be listed as a range or a "not less than" number. Also they should be tested with different levels of contrast.

The tricky part with the DSLR scanning is the assembly of the images. No lens is perfect and it's very likely there's some barrel distortion bigger than half pixel in most of the image so the only way to get a decent image is to either deal with a good amount of math or significantly overlap the shots. On the top of that chromatic aberration and vignette are issues to deal with.

Not sure if the current SLRs are including software to calibrate those parameters with non manufacturer lens.