Re: CM through Quark
Re: CM through Quark
- Subject: Re: CM through Quark
- From: Graeme Gill <email@hidden>
- Date: Tue, 13 Jul 2004 13:25:36 -0700
Chris Murphy wrote:
Compensation; or perceptual which means you're at the whim of an
unknown, undefined flavor of rendering (at least until the whole ICC v4
thing is more widely adopted and has proven itself).
And how does ICC V4 change this ?
The whole gamut mapping approach is just as fundamentally broken in
V4 as in previous versions, and no one has (nor probably should) attempt
to standardize gamut mapping algorithms, and certainly haven't in V4.
The issue of absolute/relative conversion was addressed to some degree
in V4 (providing a mechanism for a profile to unambiguously define how
it converted from absolute to relative), but the previous ambiguities
affected only absolute intent to a significant degree.
It seems to me that the underlying issue you refer to above is the
broken gamut mapping in ICC. Perceptual renderings in ICC are often
configured (by the profile creation package) to map from RGB like gamuts
to the destination, making for a poor result when converting from CMYK.
One workaround is to select relative colormetric rendering, since if the
output device is CMYK, then the source and destination gamuts roughly
match, and clipping (relative colorimetrc intent) gives a better result
than compression (perceptual intent configured for RGB like source space).
The most obvious defect (from your description) is the luminance range mismatch
(since no proper gamut mapping is being done), and "black compensation" is a
workaround for this particular defect (or a simple tailored luminance only
gamut mapping).
Graeme Gill.
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