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: filmscanners_owner@halftone.co.uk
> [mailto:filmscanners_owner@halftone.co.uk]On Behalf Of Preston Earle
> Sent: Thursday, September 11, 2003 1:58 PM
> To: austin@darkroom.com
> Subject: [filmscanners] Re: 8 bit versus 16
>
>
> Of interest in this discussion:
>
> it-16-bit.htm
> and
>
> 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
> PEarle@triad.rr.com
>
> (Still in Group 3.)
>
>
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