Martin Weberg wrote:
2007/9/17, Klaus Karcher <lists@xxxxxxxxxxxxxxxxx <mailto:lists@xxxxxxxxxxxxxxxxx>>:you know that I am sold on argyllcms, but to puzzle out the right black generation parameters sometimes drives me nuts. Me too.here is a screenshot of "xicclu -g -fb -ir SC_paper_bas.ICC": <http://digitalproof.info/argyll/black_gen/xicclu_-g_-fb_-ir_SC_paper_bas.png <http://digitalproof.info/argyll/black_gen/xicclu_-g_-fb_-ir_SC_paper_bas.png>> I get a reasonable match using: profile -qm -kp 0 .24 .98 .98 .55 -l270 -L98 -cmt -dpp fogra40l_270_98 xicclu -g -fb -ir fogra40l_270_98.icc
mmmh, looks smother then ever :-) ... but I'm amazed about the low Kmax: xicclu -fb -ir F40...-l270-L98.icc: 0.0 0.0 0.0 [Lab] -> Lut -> 0.639593 0.592091 0.496326 0.885713 [CMYK] xicclu -ff -ia F40...-l270-L98.icc: 0.639593 0.592091 0.496326 0.885713 [CMYK] -> Lut -> 18.134765 1.302415 0.341491 [Lab] I'm looking for a "landing point" close to this patch: SAMPLE_ID 1401 CMYK_C 60 CMYK_M 45 CMYK_Y 45 CMYK_K 100 LAB_L 15.61 LAB_A -0.03 LAB_B 0.75 TAC 250apparently, everything else than -L100 causes Kmax to decrease dramatically, e.g.:
xicclu -fb -ir "F40 -qm -kp 0 .24 .99 .96 .80 -l295 -L99.5.icc" 0.000000 0.000000 0.000000 [Lab] -> Lut -> 0.769063 0.681621 0.657291 0.885683 [CMYK]I don't know how the "magic" black generation code works, but it looks like -L and -l are "snaping in" on several particular locations.
Little more tweaking can be done I think.
after another dozen of trials, I think I got it now.at least the neutral axis of the perceptual intent looks smooth and reasonable:
<http://digitalproof.info/argyll/black_gen/F40-qm-kp_0_.24_.99_.995_.78-l285-L100-ip.png> <http://digitalproof.info/argyll/black_gen/F40-qm-kp_0_.24_.99_.995_.78-l285-L100-ir.png> and Lmin is pretty low: xicclu -fb -ip "F40 -qm -kp 0 .24 .99 .995 .78 -l285 -L100.icc" 0.000000 0.000000 0.000000 [Lab] -> Lut -> 0.591070 0.565901 0.552014 1.000000 [CMYK] xicclu -ff -ia "F40 -qm -kp 0 .24 .99 .995 .78 -l285 -L100.icc" 0.591070 0.565901 0.552014 1.000000 [CMYK] -> Lut -> 15.070250 0.942825 1.467935 [Lab]
Maybe you didn't want a perfect match but I hope this helps anyway.
It did, Thanks a bomb :-) Klaus