DIY DSLR Scanner vs Drum Scanner

[Peter De Smidt]

Using a template in PTGui gives very good stitches.

Resolution is complex. In what direction? At what contrast? And so on. For instance, my Cezanne has higher resolution in one direction than in the other. I don't have the time or inclination to run tests to counter every conceivable objection.

The results of my dslr BW scans are significantly better that I achieved with a consumer flatbed, and I spent a lot of time optimizing those flatbed scans. The dslr scans are almost as good as I can do on my Cezanne. The limitation is my D600. Daniel got over 5000 dpi results with a D7000, Rodenstock Magnagon and a high res target. The targets are available. Interested parties can buy one and test their own scanner. What do you get when you set the scan size to 4x5"?

[onnect17]

Resolution in CCD based systems should be higher in the center and lower and equal on the corners. If there is any difference between corners at the same distance of the center then there's an alignment problem.

I own both, the Magnagon 75mm f5.6 (fixed) and the Apo-Rodagon 75mm f/4 D. At 1:1 and f/8 the later should perform as good as if not better than the Magnagon for color applications. The only advantage of the Magnagon is the bigger circle of image, less falloff, and better performance at multiple magnification (contrary to the 0.8X to 1.2X range in the Apo-Rodagon). In any case, both lens can resolve a lot more than the capabilities of the sensors in those cameras so the resolution itself will be limited by the magnification.

I know this does not apply to your BW scanning (assuming you are using an white light source, of course) but others scanning color via DSLR should keep in mind the sensors in question are designed using the Bayer pattern so the real sampling is half and 3/4 of the megapixels are product of interpolation. So in order to sample for real an area in color at 5000 dpi with the D7000 sensor it's necessary to use a magnification of almost 2x. (209 pixels/mm divided by 2 ==> ~105 pixels/mm ==> ~2650 pixels/inch).
So let's say we want scan a 35mm negative with the D7000. Half of the sensor size is 23.6mm/2= 11.8mm ==> 36/11.8mm = ~3. Then 3x3=9 so it will be necessary to take at least 9 shots without overlaping to complete the frame.

This is not an issue with tricolor or monochromatic linear CCDs used in some professional scanners. Not familiar with the Cezanne but it seems to use the same Kodak chip as the Imacon.

[Peter De Smidt]

And this discussion helps the original poster in what way? All we know is that he is getting more "grain" in his scan than he'd like. If it truly is due to grain aliasing, we know that increasing the resolution of his scan will help. Neither Daniel nor I have noticed this problem with our dslr scans. While I mainly scan BW, I have scanned color slides and negatives, and Daniel mostly scans color. A priori complaints about Bayer sensors just muddy up the issue. Why not post them in the appropriate dslr scanner thread? It would be: http://www.largeformatphotography.in...t=dslr+scanner Or better yet, why not hold off on that until you have some empirical tests that support your theorizing?

Both Daniel and I have posted the scans of our resolution targets. They give clear results in two directions. That is the basis for our claims. We have checked both the center and all corners of the frame.

[onnect17]

I don't think there's any "theorizing" in my post. The numbers are taken directly from Nikon specs.

But talking about theory, how this could help the original post? Very simple.

He has to know the real sampling frequency to avoid getting close to the size of (or a multiple of) the grain in the emulsion. This is very important with Tgrain type emulsions (most of the modern emulsions) where the grain size is very even. A very common approach to address the problem is to reduce or increase the sampling resolution by 50% where possible.

He should know every single aspect of the technology in the camera that could impact the resolution in the image, Bayer, antialiasing filter, etch.

He should be able to recognize the grain. Many times there is some degree of sharpening applied to the image without the user being aware. The grain in the color film is red, green and blue. If you see anything else then check for unintended sharpening or processing.

I am glad to hear you and others are happy with the results being obtained with the DSLR based scanners. However it was not being totally happy with the results the reason why I explored many scanning technologies until I settled with drum scanners, and the cost for most of them was between $500-$1000, which I guess is lower than the cost of a D600.

[Peter De Smidt]

"He should know every single aspect of the technology in the camera that could impact the resolution in the image, Bayer, antialiasing filter, etch."

So the same applies to you before you do anything? You understand _everything_ before doing anything? So you get a lot done?

The theorizing isn't in the regurgitation of Nikon info. The theorizing is in how that information impacts scan quality, and in particular how that info is a problem (or leads to a solution) in this case.

Again, to summarize:
1) The poster has a problem with excessive "grain."
2) Other people with dslr scanners with Bayer pattern sensors don't have this problem.
3) Therefore the problem isn't with Bayer pattern sensors in general.

The proper way to approach this problem is clear. First, we need to find out how the original poster is doing his scans. For instance, it doesn't look like he's using a good lens or magnification for this task, but more info will clear that up. With that info, the answer might be obvious. If it's not, he can send some film to me. I'll scan it on both a dslr scanner and on a Cezanne at 6000 spi. That would tell him whether he wants to pursue dslr scanning or not. If someone else wants to offer up their valuable time and scan the film on a drum scanner, well, that'd be helpful.

The dslr scanner project has taken years to get to this point. All along the way, critics would pop up repeating the same old complaints. Then we showed samples, and they went away for a little bit.... Does this mean that dslr scanners are without flaws? Absolutely not. But the scans achievable are clearly better than what's possible with an Epson flatbed, which isn't to say that they can't give good enough scans for some purposes.

It's similar to the situation with drum scanners and pro flatbeds. Some people dismiss the flatbed scans, as PMT scanners, they hold, are inherently superior. But then you have someone like Tim Parkin acquire a large number of the scanners and use them. He finds out the some of the flatbeds are better in some regards than the drum scanners.

Here's another example. I bought a D200 when they came out. Over the next few years, lot's of theorists bemoaned increasing resolution, mostly because they enjoyed bitching about something, but in part because the sensor sizes were getting smaller, and it was "a law of physics" that smaller sensors would lead to less sensitivity, less dynamic range and more noise. Well, a while ago I bought a d600. Despite have much more resolution than the D200, it has significantly better sensitivity, dynamic range and freedom from noise. Obviously there's more to the equation than the sensor size. Experience trumps theory.

[onnect17]

On the contrary. My approach to scanning devices is that I never know enough, so I try to learn as much as possible about the technology behind, sometimes bringing the equipment near the danger zone.

There is not such a thing as a perfect scanning device. The more we learn about the shortcomings the easier it's to judge the resulting image, and many times theory and heuristics challenging each other. It also helps setting expectations. I use it positively and have a lot of fun.

Perhaps Jason is confusing large size grain with grain aliasing. The first link shows a high speed film with the expected large size grain. I am unable to see any aliasing issue in the image. The lens is not the issue, for sure. The 50mm f/1.8 is not a macro lens but it’s good enough for the tests. He’s more than welcome to get in touch via PM.

[Peter De Smidt]

Jason,

What light source are you using? At one time I had a Coolscan V, which had a fairly small LED light source. With fine-grained films, it thoroughly trounced my Canonscan 9950F flatbed, which had a large and diffuse light source, but with course grain film the Nikon exaggerated the grain tremendously. So with things like Kodak HIE, a very coarse-grained film, the Canonscan did a much better job.

[JasonF]

A lot of great questions! When I get a better chance (which I don't have at the moment), I'll answer all these questions. I plan on posting a few scans so you can see what I see. And, I'll be provide a lot more detail on this soon as to what I'm using too. Then you can help me determine what the issue is that I seem to face.

[Bruce Watson]

...my hope, was that a DSLR scanner could at the very least match a drum scanner if not surpass it.

ROFLMAO! Thanks, I needed that!

There's always hope. My hope is that a rich relative will leave me millions, that my curious genetics will suddenly become "normal", that politicians and corporations will come to their senses and decide that "endless war" is a really stupid policy, and ... well, there's always hope.

I guess you're hoping for a change in the laws of physics. Good for you; there's always hope.

[Peter De Smidt]

Yeah, I have to agree with Bruce on that. My goal was to better an Epson scanner. No problem. But the dslr scanner is not as good as my Cezanne, let alone as good as a drum scanner when it comes to d-max.