[argyllcms] Re: Gamut mapping problems in 1.1.0

  • From: Klaus Karcher <lists@xxxxxxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Mon, 09 Nov 2009 00:46:23 +0100

Hi Martin,

you wrote:
I'm using Argyll_V1.1.0_RC1_osx10.4_i86 and the gamut mapping isn't working properly for me when building RGB to CMYK device link profiles.

Everything works as expected until either -g or -G are used. The results are not any better when using source image gamuts either.

There is a loss of saturation immediately noticeable throughout the resulting images.

Images which are highly saturated -- the seaside sunset image in Bill Atkinson's Lab Target for instance -- will not give an acceptable result if any type of gamut mapping is used.

How did you use tiffgamut and collink -g / -G on Bill Atkinson's Lab images? Did you convert them to RGB? How? Which RGB? Did you cut-out the individual images before using tiffgamut? (this will make a big difference!) Did you try tiffgamut -f?

I'm still testing the new gamut mapping but I think there are some great improvements compared to previous versions. You are right: there is less saturation than in 1.0.3 or 1.0.4, but there are also much more details preserved in saturated areas (e.g. in my red flowers example). While my attempts to improve the gamut mapping parameters in GaMapICC 0.3b caused overdone brightening in some saturated colors, there seems to happen the opposite in 1.1.0 RC1 (e.g. with roman16_red and ISO coated v2).

Maybe this issue is related with a separation bug I noticed in conjunction with collink's -ke flag: I generally get much more black (and less CMY) than expected when I use collink -ke. There is e.g. no cyan at all in skin tones, not even in the shadows, where I'd expect 20-30% cyan with a normal ISO Coated v2 separation.

I guess Graeme is on the way to Albquerque [I envy him!], so I think we have to wait at least one week before he can see about this issue.


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