Re: Decimal precision in Photoshop's info palette
Re: Decimal precision in Photoshop's info palette
- Subject: Re: Decimal precision in Photoshop's info palette
- From: Karsten Krüger <email@hidden>
- Date: Fri, 19 May 2006 09:38:44 +0200
Am 19.05.2006 um 08:45 schrieb Marco Ugolini:
In a message dated 5/18/06 5:28 PM, CS Carl Stawicki (4211) wrote:
Yeah, RGB gives you those high precision numbers, but I never
understood why.
To me, 8-bit should mean integers from 0-255. There's more going
on under the
hood than I understand.
:: snip
2) Click on the color picker's foreground patch, and enter the
following
color values in the Color Picker dialog box: C 14, M 89, Y 64, K 22;
:: snip
6) The results this time will be {class:CMYK color, cyan:14.12,
magenta:89.02, yellow:63.92, black:21.96}. The colors have shifted,
albeit
slightly, but nonetheless they are not exactly what they are
supposed to be.
In some way Adobe has to translate 0..100 into 8 bit notation 0..255.
This is
what you see here, I guess. Try in 16bit mode. Do you get different
values ?
:: snip
In Lab, the values entered by hand as integers are shown as
integers when
retrieved with the script, but after the fill-resample routine, the
L* value
shifts slightly, while a* and b* remain unchanged.
L has the same issue like above.
a and b are floating point, so the math is slightly different.
Did you try 16 bit Lab or 8 bit Lab ?
This all feels very puzzling and inconsistent to me. It may have
something
to do with the "quantization" problems I have heard mentioned at
times in
imaging circles, perhaps? But then, why the different behaviors in
different
color modes?
Because of 8 bit or 16 bit mapping of decimal values (0..100).
Just for understanding (and talking about RGB or CMYK, not talking
about Lab):
- can you really see those .x differences in color on your monitor ?
- can you print those differences on your printer and actually see
the differences in the printout ?
If the answer to both questions is yes, then I would like to know
more about your equipment.
Karsten
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