if stuff on the web displays (generally) only in 24bits, and i think PS
and other image editing software also works in 24bits, what's the use of
scanning at higher depth? if there were two pictures, side by side, 24 and
36 (or 32, if the monitor is limited to 32), can one visually discern
it?
The only useful reason to scan at higher bit depths is if you are
going to manipulate the image, especially the value curves.
There is no visible difference between the two initially, but
differences can build up more readily in 24 bit images when you apply
multiple edits.
For example, let's just say you have a B&W image with a value range
of 1 to 100, but only values from 26 to 75 are represented. You
adjust the curves to "normalize" the value range, perhaps through
auto levels or auto contrast. The image values now have a "comb" look
in histograms, with all the odd or even values missing.
Now lets say you do your value adjustment on a scale from 1 to 1000
on values that range from 261 to 750. Afterward, you still have
combed data, with only even or odd values, but now you reduce it to
the "normal" 1 to 100 range, and every value is represented.
For the best precision, do as much editing you can in 48 bits --
especially global curves -- then reduce to 24 bits. Of course,
scanner software is supposed to do this.
--
: Jan Steinman <mailto:Jan@xxxxxxxxxxxxxx>
: Bytesmiths <http://www.bytesmiths.com>
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