[argyllcms] Re: Conversion omitting/locking device colorant
- From: "Martin Weberg" <martin.weberg@xxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Wed, 14 Jan 2009 12:21:02 +0100
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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