Re: Lab in Photoshop
Re: Lab in Photoshop
- Subject: Re: Lab in Photoshop
- From: bruce fraser <email@hidden>
- Date: Fri, 12 Jul 2002 09:46:14 -0700
At 9:32 AM -0700 7/12/02, Dick Busher wrote:
> Bruce J. Lindbloom wrote:
With regard to Adobe 1998 specifically, there is only a very small amount of
clipping that will occur (pure Adobe 1998 green maps into an Lab value whose
a* value is -129, which is just barely outside the Photoshop range limit of
-128; all other parts of Adobe color space fit inside Photoshop Lab).
However, there will be some quantization of colors on the inside of the
gamut, but this is not "clipping." With other larger working spaces, such as
ProPhoto, clipping will be more severe.
Am I correct in my understanding that rgb to cmyk conversions are
rgb-Lab-cmyk?
Nope. All the CMMs I'm aware of build a table that goes directly from
RGB to CMYK, using Lab only as the reference.
If that
is the case, then will cmyk separations from large gamut spaces such
as Ektaspace always
result in some clipping?
Yes, but not from the PCS, just from the CMYK space (unless you're
using inks that give you a suntan).
Should we limit ourselves to Adobe rgb when cmyk separations for
offset is the end product?
Unless you're creating synthetic material in a wide-gamut space, or
doing some very heavy-handed editing, the boundedness of ICC Lab is
really a non-issue. It certainly contains all colors you're likely to
capture from the real world. If you're exposing film or CCDs to
monochrome lasers, you might conceivably run into an issue, short of
that, you won't.
--
email@hidden
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