scanning with dslr?

[Sevo]

I do occasionally make "scans" with a Laborator, Componon-S, Sinar and Phaseone scanning back whenever there is a colour cast or (extremely low or high key) exposure that seems to drive my flatbed beyond its limits. Too time consuming for non-critical work, but this actually works out very well - but then, that is rather high-end gear and not really that far off its intended use.

But I don't know whether usual DSLRs have sensor side contrast control - if you have to compensate for the double Gamma increase in postproduction, you'd lose too much contrast bandwidth to stay on a level with a decentish flatbed. A pro DSLR with pro grade macro lens might do as a replacement for a upper end consumer scanner - but it will hardly be on a par with a similarily priced scanner, and the $300 DX SLR with kit zoom will probably be much worse than a $300 scanner.

Sevo

[Bruce Watson]

exactly thatswhy i am asking. i had an idea but no real world experince. i also can't prove nothing because of the lack of equipment.
what i have is an itching idea...

People have tried this kind of thing before. What I've read says that the big problems are consistent, color correct, full spectrum lighting edge-to-edge over the film, along with alignment issues in keeping the sensor plane of the camera oriented exactly parallel to the film. It's an order of magnitude more difficult to maintain the sensor plane relative to the film plane when you are moving the camera. It would take fairly hefty and complex tooling to facilitate this motion of the camera while maintaining the required alignment to the film.

When you think about it, that's pretty much what a flatbed scanner is already -- the correct lighting, plus a fixture to hold and move the CCD array across the film. A drum scanner is somewhat different, but similar in its own way -- again the correct lighting, but this time with a fixture to hold and move the film in front of the sensors (mirrors, splitters, and the PMTs).

[Ben Syverson]

I think the key is that you DON'T move the camera. The camera stays fixed, and you move the film on the light box.

I don't see any reason why this wouldn't work, but jeez, it sounds rather labor-intensive and error-prone!

[walter23]

Before I got my scanner (Epson V750) I copied negatives in this way, with an 8MP DSLR. My technique was to lay a clean piece of glass across supports above a white light source (piles of books on each side of my laptop's monitor, set to a blank white page in firefox - ie, location in the URL field == about:blank). I suspended the negative so that the pixels of my laptop's monitor wouldn't be visible (blurred out into a uniform white light source). Make sure all the room light is gone (I did it at night in a darkened room) so that there are no reflections off the front of the film surface; you only want to shoot transmitted light.

It worked well and I probably could have made prints about as good as from my DSLR with it (ie, you don't gain any 4x5 advantages except for the movements!). I suspect even a 4 shot stitch would be technically challenging. Sliding the film around would probably be easier to manage than moving the camera (which would presumably be on a tripod pointing down; difficult to move precisely in this configuration).

[boris]

"you don't gain any 4x5 advantages except for the movements."

why can't i achieve the quality of my lf negativ by copying it?
when i examine through a loupe it's sharp, when i enlarge it is sharp, when i copy it...
deep in my heart i know it is impossible, but i would like to understand why?
boris

[Andrew O'Neill]

Yes, you can.

[David A. Goldfarb]

When I've done it, I've kept the camera in one place and moved the lightbox around on the baseboard of the copy stand. Photomerge needs a fair amount of overlap to work well, I find, so 9 shots is actually less labor intensive than 4 shots that don't overlap as much and fiddling with the stitch.

I've posted an example from a 9-tile stitch from a 35mm transparency with a discussion of the technique and equipment used over at--

http://www.hybridphoto.com/forums/showthread.php?t=555

There are a few areas where I can improve on that result, but it's already better than what I can get from my old 35mm film scanner (Minolta Scan Dual I).

[QT Luong]

I've tried it before. Although I use good DSLRs, the results have been lacking with respect to color and contrast. In the end, I just send out for drum scans. The best rationale for drum scans was provided by Lenny in another thread: removes one variable, since you know you've done the best you could on this part of the imaging chain.

[Gordon Moat]

You might search this forum, where someone within the last two years did exactly what you proposed. He matched that up by trying scanning the same 4x5 film with low end Canon, HP, and Epson scanners.

The main problem was not resolution, since with stitching you can get close to the resolution, given and lens and sensor combination that work well. The biggest downside was the contrast was increased, and the colour balance were altered. All shadow areas went to black, unless you risked blowing out highlights.

I think it might be possible with B/W films, but I would not try it with colour. The best result you could expect would only be good enough for viewing the images on the internet. Resolution is not the problem of such a DSLR set-up, but colour and contrast are huge issues. I would never make such a bad choice compromise.

Ciao!

Gordon Moat Photography

[Nathan Potter]

"you don't gain any 4x5 advantages except for the movements."

why can't i achieve the quality of my lf negativ by copying it?
when i examine through a loupe it's sharp, when i enlarge it is sharp, when i copy it...
deep in my heart i know it is impossible, but i would like to understand why?
boris

Boris, IMHO you can come close to achieving the intrinsic quality that is in your 4X5 neg or chrome. It just takes a highly optimized setup to do it. You have to take into account all the issues mentioned above. Re - even backlighting, critical focus, high resolution macro rectilinear lens, high stability, accurate image translation. One really ought to have a dedicated setup specially designed, maybe not unlike the old Bowens Illumitran (sp) copy setup but more sophisticated. Even then there is an issue of what dmax can you record with, presumably, a low intensity backlight (need long exposures) and as Sevo points out you will suffer a gamma increase (OK for some material of low contrast) and at the end you still have to combine images.

Nevertheless people are fooling around with this.

Nate Potter, Austin TX.