Of interest in this discussion: http://www.ledet.com/margulis/ACT_postings/ColorCorrection/ACT-8-bit-16-bit.htm and http://www.ledet.com/margulis/ACT_postings/ColorCorrection/ACT-16-bit-2002.htm
Money quote from Dan Margulis: "The bottom line of all my tests was, with one important caveat that I'll get to in a moment, there is no 16-bit advantage. I blasted these files with a series of corrections far beyond anything real-world; I worked at gammas ranging from 1.0 to 2.5 and in all four of the standard RGBs, I worked with negs, positives, LAB, CMYK, RGB, Hue/Saturation, what have you. While the results weren't identical there were scarcely any cases where there would be detectable differences and in those one would be as likely to prefer the 8-bit version as the 16. So, I have no reservation in saying that there's no particular point in retaining files in 16-bit, although it doesn't hurt either. I'll show all these results later, but the surprise was in the files that Ric [Cohn] sent, which appeared to show just the sort of damage that 8-bit editing is supposed to cause, in an image with a dark rich blue gradient, a worst-case scenario in conjunction with the very dark original scan, which in itself was an attempt to give an advantage to 16-bit editing. Ric provided both original 8-bit and 16-bit versions of these files. Granted that the necessary corrections were very severe, they still showed that what he said was true: the 8-bit version banded rather badly and the 16-bit did not. I tried several different ways of trying to get around the disadvantage and could not do so without excessive effort. Ric's 8-bit original, however, was generated from the 16-bit scan not by Photoshop but rather within his own scanner software. Therefore, I tried further tests where I applied the same extreme corrections to the image, but this time not to Ric's 8-bit image but rather a direct Photoshop conversion of Ric's 16- bit image to 8-bit. Shockingly, this completely eliminated the problem. There was no reason to prefer the version corrected entirely in 16-bit. When Photoshop converts from 16-bit to 8-bit it applies very fine noise to try to control subsequent problems. Most scanners don't. I would have expected this to make a difference but not to the point that the scanner 8-bit file would completely suck and the Photoshop 8-bit file would be just as good as the 16- bit version. I don't know whether this is all a function of Photoshop's superior algorithm or whether the scanner is doing something bad. Furthermore, I don't care. One way or another, the 8-bit scanner file is bad and the 8-bit Photoshop file is good." Preston Earle [EMAIL PROTECTED] (Still in Group 3.) ---------------------------------------------------------------------------------------- Unsubscribe by mail to [EMAIL PROTECTED], with 'unsubscribe filmscanners' or 'unsubscribe filmscanners_digest' (as appropriate) in the message title or body
