Re: "Proper Gamut Mapping"
Re: "Proper Gamut Mapping"
- Subject: Re: "Proper Gamut Mapping"
- From: Roger Breton <email@hidden>
- Date: Sun, 16 Dec 2007 10:07:21 -0500
> So gamut mapping would be improved by building a device link for the specific
> source gamut-destination gamut combination.
Such as in Argyll's DVL. Or using one of the Perceptual Reference Gamut PCS
like the one currently in the works for sRGB. Or using Vista CMS, which
isn't much farther than when it came out two years ago.
> Or, if the profile making
> applications would let us, by specifing the expected source gamut before
> building the B2A0 table in a conventional ICC profile, and then the user
> ensuring that the colour data to be converted are in that expected
> colourspace.
Isn't that ideal? I once asked Heidelberg that very question but did not get
the reply I was looking for. This possibly could be asked to all profilers
but I'm not sure the answer is going to be along the lines we'd expect. I
suspect the better profilers use a little more complex heuristics.
> The v4 ICC spec improves this situation by specifying the source gamut
> explicity.
How? Care to quote the relevant part of the spec?
> To improve further, because, say, the gamut of the colour values comprising an
> _image_ would rarely fill the entire gamut of the colourspace to which the
> image belongs, the ideal scenario would be image-specific gamut mapping
> calculated at the time of conversion to a destination profile. This is the
> very idea of a "smart" CMM, if my understanding is correct.
The only thing that comes close to this today, commercially, that I know of,
is Fuji C-Fit. Along with offering support for the regular ICC RI it offers
is own flavors of Perc and Col RIs such that it calculates the gamut mapping
dynamically for every image that comes along extracting the data out of the
chosen Source and Destination profiles. Plus it incorporates a number of
advanced proprietary color tweaks that result in very different kinds of
separations, with loads of local perceptual and colorimetric and saturation
optimizations for memory colors and lightness mapping. I hope to post some
sample images on my web site soon...
> Matthew Larmour
Roger Breton
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