Digital BW, The Print

Thanks for the information, Bob.  But whereas from
following these lists for years I know that you (and
others) are an accomplished photographer, I, as a
photo restorer, have several images where the
difference between working in 8- vs. 16-bit mode has
been astounding.

Now remember, I restore old photos -- lots of massive
"corrections", including the black and white points in
"Levels".  I have a B&W image from 1951, for example,
that I worked on within Photoshop 6 or 7 (I can't
recall which), but that I recently had reason to
revisit.

I rescanned the original image then worked for three
days to restore it, with Photoshop CS in full 16-bit
mode.

In Photoshop, the 8-bit version's histogram looked
awful (I'd be embarrassed at this today), whereas the
histogram in under the 16-bit version was very smooth.


In comparing the old and new print outputs (both from
my HP 7960 in grayscale mode), the difference was
significant.  The print that I restored in 8-bit mode
was MUCH grainer and exhibited significant small areas
of posterization (sp?).  In comparison, the 16-bit
version printed as smooooooth as a baby's butt
(without diaper rash).

I need to again note that we are dealing with a
restored 1951 image that required massive tonal
corrections, a "Multiply" blending mode, and need to
use "Curves" to improve contrast.

The only remaining issue for me is whether to now
keep/store such images in 16-bit mode, given how huge
the file sizes are.  Here is where I might agree that
since the major work has been done, any future work on
the image is likely to be limited to minor tweaks to
optimize printing for some future printer.  It is
unlikely that for such tweeks 8- vs. 16-bit would make
any difference.

That's my take.

Howard


--- Bob Frost <bob@...> wrote:

> Howard,
> 
> I think most experts agree that one can see the
> advantages/effects of
> working in 16bit on the screen in the pixels of the
> image and in its
> histograms, but where they still seem to disagree is
> whether these numerical
> advantages of working in 16bit can be seen in the
> final print. If not, why
> do it?
> 
> On the Colortheory list this topic comes up quite
> often, and did so again
> recently. I have copied parts of Dan Margulis's
> recent comments and
> challenge below:-
> 
> 
>     "What I and other people have said is that we
> have tried to produce 
> imagesdemonstrating that applying adjustments to a
> real-world color 
> photograph in 6-bit could produce a better result
> under any conceivable set 
> of
> real-world circumstances, however far-fetched, than
> doing the same thing in 
> 8-bit. So far, however, we haven't been able to do
> it in even a single 
> image, despite having used exactly the sorts of
> images and the sorts of 
> maneuvering that we have been assured produces a
> night-and-day, totally 
> obvious,
> you-are-a-recreational-user-if-you-don't-do-this
> difference.
> 
> Because I have given up on ever finding an image
> myself, I am reduced to 
> hoping that someone like yourself can find that
> elusive single image which 
> will demonstrate that 16-bit is better under at
> least some real-world 
> circumstances.
> 
> .............................
> 
> However, if you (or any other list member) ever does
> happen to run
> across such an image, you are most cordially invited
> to notify me offline so
> that we can make arrangements to verify it and put
> it out there for people 
> to see. This would be a significant service to
> everyone. If there is in fact 
> a point where the use of 16-bit might become
> desirable, I'd certainly like 
> to tell my classes about it.
> 
> As always, my only requests would be that it be a
> color photograph,
> however bad or unusual, that might conceivably be
> used by itself in 
> professional context; that the steps or series of
> steps taken to "correct" 
> it,
> however incompetent, are at least conceivable; and
> that the provider be 
> willing to release it for publication to demonstrate
> the limited point of 
> whether 16-bit correction can ever serve any useful
> purpose at all.
> 
> Dan Margulis"
> 
> 
> So, Howard, if you really do have prints that show
> the beneficial effect of
> having been worked on in 16bit, then you could
> become even more famous than 
> you already are! Just send Dan two prints of the
> same image, with the same 
> treatments, one done in 16bit and the other in 8bit,
> along with the files 
> for verification.
> 
> Bob Frost.
> 
> ----- Original Message ----- 
> From: "Howard Averbach" <haverbach@...>
> 
> >
> > For what it's worth:  unlike photographers, whose
> > camera output is likely "pretty good" to begin
> with
> > and thus needing mere tweeking and croping, photo
> > restorers like myself typically start with
> horrible to
> > fair originals that need MASSIVE "Levels"
> adjustments,
> > lots of "Cloning", and often extensive color and
> other
> > improvements.
> >
> > In situations like this, ANYONE can see the
> > significant improvement -- to the histogram as
> well as
> > to the final output -- using 16-bit files as
> opposed
> > to 8-bit mode.
> 
> 



		
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