Since my old Duoscan got too streaky to use anymore about six months ago or so, and I didn't want to get involved in cleaning it, I decided to replace it with a Canon 40D and come back to my digicam scanning method, this time with a better camera and lenses.
So far it's working pretty well, and this evening I figured out how to do better with the 40D than with my dedicated 35mm film scanner--an old Minolta Dimage Scan Dual. Camera on copystand, 5000K lightbox, Canon FD 35mm/2.8 Macrophoto lens (a lens for high magnification like a Zeiss Luminar or Leitz Photar) at f:5.6, and a 9-panel stitch using Photomerge in CS2. I still have a little refinement to do on alignment and finding the optimal magnification, but I was able to get a 7334x4975 pixel file that's unquestionably sharper than the scanner can produce, and with 9 panels, there's enough overlap for Photomerge to do its thing without having to do any fiddling, and I found that the final image benefited from very little additional sharpening.
Here's the full image--
and here's a 100% crop from the center--
I tried 4 panels at first, and it wasn't enough for a good stitch. I also tried a single frame with a Tamron SP 90/2.5 and the corners weren't quite as sharp as the scan, though the camera produces a larger file than the scanner, so there's some room for sharpening.
The downsides are that stitching 9 images is fiddly compared to using a scanner, but I don't need to do it that often, so I'd rather reclaim the desk space and get rid of another scanner, and if I want 16-bit Photomerge, I guess I've got to upgrade from CS2. Computer timewise, I think a 4-pass scan with the Scan Dual in Vuescan is comparable to the time it takes to stitch nine 8-bit RGB TIFF files from the 40D.
Incidentally, I recently sold my 25mm/3.5 Zeiss Luminar for almost the full price of my second-hand 40D, because the more modern Canon FD 35mm Macrophoto is really a sharper lens and gives a little more working distance, but of course the Canon isn't as collectible, so you can usually find it for less than a Luminar. Both are RMS screw mount, but the Canon comes with an FD adapter, which I'm using with an FD-EOS macro adapter and FD extension tubes. You can find RMS-M42 adapters on eBay, and then adapt from M42 to most camera mounts.