At 08:10 AM 9/24/00 -0700, you wrote:
>>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.
They don't dither? They should - on both upconversion and downconversion.
Paul
>
>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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