Digital BW, The Print

I doubt there will ever be a need for a 32 bit camera. As things stand
right now I don't believe that there is much in the way of an
appreciable difference whether the final image is in 8 or 16 bit
values. 4294967296 (2 to the 32nd power) independent tones in an image
is complete overkill and would ridiculously bloat the size of the
files even further. As things stand right now I believe that most high
end digital cameras capture a 12 bit image 4096 independent tones.

Paul, whether the redistribution of the pixels is done by curves, the
contrast slider or other tool makes no difference. If your adjustment
causes a change which exceeds the amount of headroom between each
discrete tonal value then you are going to reduce the number of
independent tones in your image. In an image that begins with 256
tones in an 8-bit space then your headroom is 0, while in a 16-bit
space your headroom is 255. An image that begins with 128 (evenly
distributed) tones in an 8-bit space has 1 bit of headroom between
values, while in 16-bit land it would have 512 bits of headroom.

Please keep in mind that I've massively simplified how these things
work in the real world. A contrast adjustment is not likely to be a
simple subtraction/addition of a single value to all pixels in the
image not equal to the midpoint.

Maybe I should take the time to write a full fledged article on how
this stuff works.
--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Paul Roark"
<paul.roark@...> wrote:
>
> Derek,
> 
> >A little bit of computer science here.
> 
> >... lets say that you adjust the global contrast of your image. ...
> > In an 8 bit file if we subtract 1 from each value less 
> > than 128 then we now have 126 tones where we had 127 tones 
> > before the subtraction. This is because the pixels that were 
> > formerly at value 1 are now at zero ...
> 
> If you'd used curves for this adjustment, would there have been any
loss?
> 
> Paul
> www.PaulRoark.com
>