Making a scanner with a DSLR

[Brian C. Miller]

Oh, yeah, and servos on the camera mount for auto alignment. Don't want to forget that one!

So what you really want is a drum scanner, but you'll settle for a computer-controlled copy table adapted to a digital camera. Not at all difficult.

The Open Camera Controller can be a start on how to control a DSLR. The Arduino page has notes on steppter motor interface. The Gimp has a batch mode and ScriptFu that can stitch the images together and do some other stuff if you like. The rest is commodity hardware.

Hmmm, I only have a point & shoot, and I'm not upgrading just yet.

[Brian C. Miller]

The big questions are:
1) Can such a system provide the needed quality? (It's an awful amount of work if we can't do better than a V700.)

It can provide the quality according to the DSLR and macro lens used with it, nothing more than that. This is just an automated copy table. It can't do more than that. If the camera can focus down to the grain, then fine. Tim Parkin could shed some light on that, as he has a DSLR on a microscope. I'm guessing that a DSLR with a 1:1 macro lens won't be able to resolve the grain, but I have no personal clue.

If somebody here has a DSLR with a 1:1 macro lens, it would be easy to get some actual results.

2) Can stitching software operate successfully at the grain level? With normal sized stitches, there tends to be much more prominent image elements.

No idea. I'm guessing that it could.

[Frank Petronio]

Right now Nikon is reading this thread, quick get out the NDAs.

Eh no. Photographic companies listening to customers to make products? Hahahaha how old-fashioned.

Still... a 0.063% royalty would be nice.

[Peter De Smidt]

Well, sure I have a number of 1:1 capable macro lenses, and an enlarging lens on a macro bellows can do much more than that. But as I've mentioned, focusing at that level with my camera is a huge pain...And I already have a nice scanner, and a violin to finish making...

[tlitody]

will it work on an IPhone?

[Brian C. Miller]

Yes, it will work on an iPhone. DSLR cameras can rest comfortably on top of an iPhone and still function. Same goes for LF cameras, too. Caterpillar 797F trucks can also work on an iPhone, but after they do, the iPhone won't work!

[rdenney]

I could see slide film being a problem, but for the fact that most slide film did not have a dynamic range of greater than 6 or 7 stops, and most DSLRs can do 9 to 13 stops. (Admittedly the way dynamic range is defined on film vs on sensors is different, but...)

Slide film may only see 6 or 8 stops of subject brightness range, but it actually spreads them out to a wide range of densities, from clear film to nearly opaque. Of course, the density range of slides is intended to reflect highlights and shadows as seen in the real world. Slides are the most difficult of all to scan because of their density range.

Negatives have much less density range. I can scan both color or black-and-white negatives in an Epson flatbed without running out of range, though for really thick black and white negatives I have had to use a wide-gamut color space to avoid clipping the extremes. A digital camera should have no trouble capturing the density range of negatives.

Sensors are pretty linear--moreso than film--but one assumes it would be fairly easy to correct the scanning bias using a general tone curve adjustment. The sensors in digital cameras are certainly as good as the tri-linear sensors on scanners.

Rick "thinking we might all have to construct such tools when the existing generation of scanners pass away" Denney

[Ben Syverson]

I know the comment about iPhones was facetious, but it may be more right than you know... Within a couple years, your phone will do fantastic macro at 12-15 MP. More than enough for stitching.

From my end, it's much easier to write iPhone software that takes photos and tiles them immediately, as opposed to separate camera control software and desktop software to collate and stitch.

I still think it's a mistake to make the first version motorized. You undoubtedly WILL have stability, vibration and focus problems.

[rdenney]

Anyone could contract a system like I've described above, and retail it for under $250. If no one does it in the next year or two, Justin and I will do it...

You provide what you have described for $250, and I'll be first in line. I don't mind moving the camera manually if there are reasonable detents. I can stitch in Photoshop.

Now, as to whether it would be better than an Epson, a more refined question is what level of camera and lens would be required to beat an Epson?

Here's a modest setup: I have an old 90mm SP Tamron with its 1:1 converter that is not bad. Let's say it resolves 60 lines/mm. At 1:1, that would put 60 lines/mm on the sensor. That would take the 5D's sensor right about to its Nyquist limit with 125 sensor sites/mm. I'm quite sure that lens is good enough to do that, even though it's old and relatively cheap. But 125 sp/mm is 1600 spi.

Nope, not good enough. The Epson can do maybe 2000ish. Maybe the camera would do a better job with tonal range and so on. Maybe not. But the resolution has to be high enough to take advantage of the negative.

So, we'd need a lens that is real good at, say, 2:1, to get 3200 spi. Or a camera with a higher sensor density, but not so high that it outstrips an affordable lens. 3200 would match a high-end flatbed if it could deliver it accurately with affordable equipment.

How about a proof of concept? Can someone with a prospective camera and lens mount the camera such that a proper photo can be made of a piece of a negative with all the moving and stitchin? A 1:1 macro lens would be the baseline, with the next step up being a very good enlarger lens (possibly even reversed) on a bellows, perhaps. Let's see what real resolution we can get at different price points of lenses and cameras. If it takes $4000 worth of camera and lens to beat a $1000 Epson, interest wanes. If I get time this weekend, I'll compare my "modest" setup with a negative that I have already scanned on the Epson.

Rick "thinking the concept needs proof before building a machine" Denney

[tlitody]

Now let me see. We like to use film because of all the detail we can capture. And we like the grain in film. So now we are going to photograph the film with a digital camera which we don't like because it doesn't have grain and will not capture the grain in the film anyway, and then use the digital file to output digitally.
I have a really great idea. Why don't we just use a digital camera and cut out the film altogether. And there's this little thing called HDR which means we can get way more dynamic range than film anyway. And since we would be stitching the images of the film we can use the digital camera on a pano tripod head and stitch the images to get more resolution than even film could produce if we use the right lens and get it right.
I bet no one thought of that before. Hang on a minute, I think some people have been doing that for quite a few years. I guess we got left behind somewhere.

Or is it just the aesthetic of a scanned neg which is what we really like? You know that sort of soft look that uncorrected lenses give.