I don't recommend long pass or multiple pass scanning, unless you can verify that your scanner is high-quality enough not to soften up your images with those settings. On my Canon FS4000US, I don't even use the dust removal setting, as there is, for me, too much softening of the image. I have a workflow in PS that isn't too long and difficult to deal with dust, and if need be, I save the scan with a 64 bit RGBI (I = infrared), so that there is an extra pass and an extra layer to the image (larger file size of course), but Vuescan doesn't actually remove or alter anything; it just tells me where the dust is. I then go to the infrared channel in PS and select the dust (usually needs a curve adjustment first to completely isolate it), and apply the removal in one of many way. I haven't quite refined and settled on a "best" or preferred method for the removal.
Anyway, I like doing straight one pass scans because they give you a much sharper file from the beginning. I hate trashing any more of the image than I have to. Of course, since I shoot Velvia, I have no choice but to deal with the shadows, which would usually dictate multiple pass scans. They do give you more detail in the shadows, and, as importantly if not more, significantly reduce noise. I simply found that I cannot deal with the softening, however, so I found a much better way. I said
"better", mind you, not more convenient; it's not!
I do two completely different scans. One is for highlights, the other is for shadows. They are both one pass, however. The shadow scan is done by increasing the RGB Exposure to, say, 3 or 4. That effectively gives you a very long exposure pass, completely blows out highlights (and often a good deal of higher mid-tones), but brings out detail from the shadows that make me freakin' jump for joy! It's flat-out amazing!
Then, opening them in PS, I combine them to make a very nice, rich, virtually noiseless image, that is much sharper because I didn't use any multiple pass settings. I'll have to write down my workflow so that people can at least use it as a reference point. Until then, you can find basically what I do
HERE!
Sorry! I'm too tired to write out much more for now.
