Re: Gamut Mapping choices in ProfileMaker 5
Re: Gamut Mapping choices in ProfileMaker 5
- Subject: Re: Gamut Mapping choices in ProfileMaker 5
- From: Roger Breton <email@hidden>
- Date: Fri, 04 Mar 2005 09:21:26 -0500
Hi Marco,
> Do you mean to say that, as long as one uses Relative or Absolute
> Colorimetric, or Saturation intents, and not Perceptual, the choice of Gamut
> Mapping method is irrelevant, and has no effect on the results?
If I go by version 2 of the ICC specs, as far as I know, there are not be 36
ways of mapping colors colorimetrically. Out of gamut colors are clipped to
the boundary of the Destination gamut and all in gamut colors are mapped at
the same relative lightness, chroma and hue angle. That's it.
Or have I got that wrong?
> One thing puzzles me: I just read on the user list the other day a message
> from Chris Murphy (dated March 2), saying that in the B2A transform "there
> is gamut mapping and considerable gamut compression involved even in this
> rendering intent [i.e., Relative Colorimetric]."
That's the not the way I understand the specs. But I could be so very wrong.
I think you're in for reading the specs yourself...
> Following that observation, which seems to me to say that there are many
> possible ways to map and compress in B2A1,
I don't agree with that statement, again.
> then the choice of Gamut Mapping
> method MAY affect the B2A transform yet in any of the rendering intents
Yes, if you accept the premise that the specs give freedom for inward
mapping in colorimetric RI.
> (whereas the A2B portion works only one possible way in Rel Col,
> apparently).
Yes, that's my understanding too.
> The B2A transform, after all, is the one that creates the final
> values that, say, are sent to a printer.
Right.
> So, perhaps, the choice of Gamut
> Mapping method does have an effect on rendering intents other than
> Perceptual.
Well, I'd like to hear it from the 'horse's mouth' to believe it. Anyone
from Logo or X-Rite or Heidelberg or Fuji here?
> A bientôt.
A rivederci.
> Marco Ugolini
Roger Breton | Laval, Canada | email@hidden
http://pages.infinit.net/graxx
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