[argyllcms] Re: Warning: gamut mapping is non monotonic - may be not very smooth
- From: Graeme Gill <graeme@xxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Fri, 25 May 2012 00:36:05 +1000
Ben Goren wrote:
> What working space would you recommend, then -- especially for art
> reproduction / giclée? My
There's nothing wrong with such a space to work in, assuming that 8 bit
quantisation
is not an issue. It's just not good to create pure primary colors in such a
space,
nor to expand an images gamut to fill the space, nor to assume that the
spaces gamut == the image gamut for the purposes of gamut mapping.
These are exactly the same considerations as using XYZ or L*a*b* as a working
space.
In contrast, something like sRGB is a real world gamut, so many (most ?) images
have been rendered into that space (made to look as good as possible in that
space/use as much of the gamut as possible), so assuming that the source gamut
for gamut mapping is the colorspace gamut, is a reasonable thing to do.
> basic workflow has been to develop with Adobe Camera Raw to 16 bit ProPhoto.
> The image of the
> chart gets fed to Argyll to create a profile, and then I use Argyll to do a
> gamut-mapped
> conversion of the actual shots from that profile to ProPhoto for whatever
> post-processing is
> needed (sharpening, cropping, resizing, etc.), and then back to Argyll for
> another gamut-mapped
> conversion to the printer's profile.
No problem if you are using a source gamut that is derived from the actual
images
gamut. That's how you need to work in very large or unlimited working spaces.
Such
working spaces carry the color values, they don't define the gamut.
> I know from experience that sRGB very often introduces clipping, and I'm
> pretty sure that Adobe
> RGB doesn't encompass the full gamut of the iPF8100. I'm not familiar with
> ColorMatch, but I
> know there won't be any clipping with ProPhoto.
A good reason to use a larger gamut working space than sRGB.
Graeme Gill.
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