[argyllcms] Re: Conversion omitting/locking device colorant
- From: Roger <graxx@xxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Wed, 14 Jan 2009 07:21:53 -0500
Martin,
Are you trying to use the gray balance press calibration method through a
standard characterization chart, like ECI2002? If you do, don't forget to
use the 40m 40y for the Lab to CMY look up. This is the method advocated by
Heidelberg and is now carried into their Near Neutral Calibration Utility.
I'd wish for Argyll to also calculate some curves ...
MfG / Roger
> -----Message d'origine-----
> De : argyllcms-bounce@xxxxxxxxxxxxx [mailto:argyllcms-
> bounce@xxxxxxxxxxxxx] De la part de Martin Weberg
> Envoyé : 14 janvier 2009 06:21
> À : argyllcms@xxxxxxxxxxxxx
> Objet : [argyllcms] Re: Conversion omitting/locking device colorant
>
> Now, I tried creating a CMY-profile and it works!
>
> What I'm trying to do is a grey balance control strip to be used in
> offset printing. I want to use K=25, 50 and 75% along with the
> corresponding absolute colorimetric CMY color.
>
> From FOGRA39L data i get:
> CMYK -> Lab
> 0 0 0 25 -> 79.47 0.00 -1.61
> 0 0 0 50 -> 61.82 0.00 -1.16
> 0 0 0 75 -> 41.11 0.00 -0.64
>
> Those are the colors I want to mach using CMY only.
>
> The process:
>
> logo2cgats FOGRA39L.txt FOGRA39L_CMY
>
> I then...
> ...opened the FOGRA39L_CMY file, stripped it from all color
> combinations using K>0.
> ...deleted the CMYK_K column and renamed CMYK_C to CMY_C etc.
> ...deleted SAMPLE_NAME column and changed NUMBER_OF_FIELDS to 8.
> ...changed COLOR_REP to "CMY_LAB".
> ...changed TOTAL_INK_LIMIT to "300".
> ...changed NUMBER_OF_SETS to 818.
>
> colprof -v FOGRA39L_CMY
> peak err = 1.087684, avg err = 0.227369
>
> icclu -fb -ia -s100 FOGRA39L_CMY.icm
> 79.47 0.00 -1.61
> 79.470000 0.000000 -1.610000 [Lab] -> Lut -> 21.457424 15.578035
> 16.627781 [CMY]
> 61.82 0.00 -1.16
> 61.820000 0.000000 -1.160000 [Lab] -> Lut -> 45.086957 35.592316
> 36.159791 [CMY]
> 41.11 0.00 -0.64
> 41.110000 0.000000 -0.640000 [Lab] -> Lut -> 71.828383 61.889985
> 61.889836 [CMY]
>
> Now I got the CMY colors. Lets look up those colors in the
> ISOcoated_v2_eci.icc (based on FOGRA39)
>
> icclu -ff -ia -s100 ISOcoated_v2_eci.icc
> 21.457424 15.578035 16.627781 0
> 21.457424 15.578035 16.627781 0.000000 [CMYK] -> Lut -> 79.683228
> 0.115786 -1.67
> 1684 [Lab]
> 45.086957 35.592316 36.159791 0
> 45.086957 35.592316 36.159791 0.000000 [CMYK] -> Lut -> 61.831570
> 0.118898 -1.01
> 4533 [Lab]
> 71.828383 61.889985 61.889836 0
> 71.828383 61.889985 61.889836 0.000000 [CMYK] -> Lut -> 41.273152 -
> 0.094712 -0.6
> 13610 [Lab]
>
> The Lab colors are pretty close.
>
> So, in my grey balance control strip I use:
> K - CMY
> 25 - 21.5 15.6 16.6
> 50 - 45.1 35.6 36.2
> 75 - 71.8 61.9 61.9
>
> Done. Puh!
>
> Martin Weberg
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