Hi Preston, Great post, thanks...but again, I MUST stress, that Margulis is specifically talking about COLOR images, NOT B&W, and that distinction is VERY important.
Regards, Austin > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of Preston Earle > Sent: Thursday, September 11, 2003 1:58 PM > To: [EMAIL PROTECTED] > Subject: [filmscanners] Re: 8 bit versus 16 > > > Of interest in this discussion: > http://www.ledet.com/margulis/ACT_postings/ColorCorrection/ACT-8-b > it-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 ---------------------------------------------------------------------------------------- Unsubscribe by mail to [EMAIL PROTECTED], with 'unsubscribe filmscanners' or 'unsubscribe filmscanners_digest' (as appropriate) in the message title or body
