Digital BW, The Print

Austin-

For someone working with a digital image...is it worth converting 
from 8 bit to 16 bit for manipulation?

I do this from time to time so I can use the 16 bit Silver Oxide 
filters (you can use them in 8 bit but they are set up for 16).

With the Nikon D1's I shoot RAW and convert to 16 bit. I think it is 
very obvious that those images are better than ones converted to 8 
bit for BW. With pocket cameras that are 8 bit JPG files, I "think" I 
can see a little better quality, but have no real "proof."

What do you think?

Tom O'Connell



--- In DigitalBlackandWhiteThePrint@y..., "Austin Franklin" 
<darkroom@i...> wrote:
> Andre,
> 
> Read what he is discussing VERY carefully.  He is discussing COLOR, 
NOT B&W.
> They are entirely different in the regard he is discussing.  It is 
fine to
> use 8 bits/color for color, as you get 24 bits total (3 x 8), but 
for B&W,
> it is not as "forgiving", and you can severely degrade the image 
doing tonal
> manipulations in 8 bits/pixel.
> 
> Austin
> 
> 
> > -----Original Message-----
> > From: André Vallejo [mailto:avs@p...]
> > Sent: Monday, May 20, 2002 9:15 PM
> > To: DigitalBlackandWhiteThePrint@y...
> > Subject: [Digital BW] The old "8 x 16 bits" again...But worth 
reading!
> >
> >
> > The following post is reproduced from a message by Dan Margulis 
in another
> > web forum I join. I decided to reproduce it here 'cose even the
> > subject has
> > been discussed a lot here some time ago,it looks to me like a very
> > enlightning about the subject ,written by someone who knows a lot
> > about the
> > subject (he's the author of "Professional Photoshop-A guide to 
color
> > correction",one of the best books I've read). Sure it started a
> > long thread
> > in the forum,but that's the way it has to be...He gave me his ok 
for
> > cross-posting.
> > André
> >
> >
> >
> >
> > Shortly before leaving for Europe, I completed several days of 
work
> > comparing
> > the results of correcting 16-bit files versus performing the same 
edits on
> > 8-bit files. I'll have a full discussion of what this showed in 
my book
> > later
> > this year and will include the files on the CD so that others can 
verify
> > what
> > went on. However, since there was one finding that came as a 
surprise and
> > would cause me to change workflow in some cases, I thought I 
would let
> > people
> > know here first.
> >
> > As many of you know, there has been this ongoing debate as to 
whether
> > there's
> > merit in leaving files in the cumbersome 16-bit mode as long as
> > possible on
> > the theory that corrections will be more accurate. There are
> > those who have
> > strenuously argued that this is the only way to go, that there is 
a
> > night-and-day difference in the results, and that people who do 
things any
> > other way are rubes. None of these experts has ever shown 
anything other
> > than
> > a histogram to demonstrate that this is so, and my own tests have 
shown up
> > to
> > now no substantial difference.
> >
> > I therefore issued a challenge for those who could come up with 
any color
> > photographic image where any reasonable course of events might 
conceivably
> > show an advantage for working in 16-bit as opposed to just 
converting
> > immediately to 8-bit, and said if I could verify it I would admit 
it and
> > print the results.
> >
> > Naturally, none of the people who are so vehemently in favor of 
16-bit
> > correction had any such files to show, but some list members did, 
and sent
> > them to me. Particularly, Todd Flashner allowed me the use of his
> > scanner to
> > produce several high-bit images that were disastrously flat and 
would
> > presumably magnify any advantage that 16-bit might have. Ric Cohn
> > sent over
> > 2
> > gigs of images and an ungodly number of Epson proofs of images
> > that he felt
> > did demonstrate that working in 8-bit caused banding and other 
problems.
> >
> > 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
> > 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.
> >
> > I also don't know whether other scanners would have the same 
problem that
> > Ric's appears to have, but suspect that they might.
> >
> > The whole thing suggests to me that if one's scanner is capable of
> > generating
> > a 16-bit file, one should probably take it. Thereafter, whether
> > one converts
> > it to 8-bit in Photoshop early or late, it doesn't seem to make a
> > difference.
> >
> > Dan Margulis
> >
> >
> >
> >
> >
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> >
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