RE: Lab in Photoshop
RE: Lab in Photoshop
- Subject: RE: Lab in Photoshop
- From: bruce fraser <email@hidden>
- Date: Sun, 14 Jul 2002 10:40:12 -0700
At 10:09 AM -0230 7/13/02, michael shaffer wrote:
Correct me if I'm wrong ... this is a worrisome issue only for
many rgb=>cmyk=>rgb conversions, ... leastwise, a miniscule issue
for the "final" rgb=>cmyk print conversion(?)
It's much less of an issue in RGB-to-CMYK conversions performed by
the CMM, because that conversion uses a much higher precision (20
bits in the case of the Adobe CMM) and hence has less quantization
error than a conversion into 8-bit Lab.
Quantization errors converting to Lab vary in severity depending on
the source space, but typically you'll lose somewhere around 25-45 of
the available 256 levels. It's not automatically a bad thing, just a
trade-off you need to weigh before you convert to Lab for a
particular edit that's easier in that mode.
All editing operations lose levels -- the trick is throwing away what
you don't need, and keeping what you do -- but there's a widespread
perception that converting to Lab and back is a free lunch. It isn't,
and making such a conversion at the wrong time may hurt the image
more than the edit it makes possible helps.
--
email@hidden
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