Hello Graeme and Gerhard,
thanks a lot for your replies. Unfortunately I do not really understand this
(yet).
Here are the values for patch A1 in the reference file:
SAMPLE_ID XYZ_X XYZ_Y XYZ_Z LAB_L LAB_A LAB_B
LAB_C LAB_H D_RED D_GREEN D_BLUE D_VIS STDEV_X
STDEV_Y STDEV_Z MEAN_DE STDEV_DE
A1 2.622 1.970 0.758 15.331 10.511 2.674 8.89
15.75 1.47 1.88 1.93 1.70 0.06 0.05
And here is the corresponding line from the ti3-file:
SAMPLE_ID XYZ_X XYZ_Y XYZ_Z RGB_R RGB_G RGB_B STDEV_R STDEV_G STDEV_B
A01 2.622000 1.970000 0.758000 28.91538 19.94871 19.18301 0.720745 0.465900
0.899324
So the XYZ-data are identical. RGB_R ... are the measured values from the
target scan. This I understand.
And here is what profcheck tells me:
[1.146434] A01: 0.28915380 0.19948710 0.19183010 -> 14.802257 14.722387
13.324269 should be 15.329014 15.318528 12.124771
, but not mangled otherwise
--- Begin Message ---Am 08.06.20 um 09:04 schrieb Hermann-Josef Röser:
- From: "Gerhard Fuernkranz" <nospam456@xxxxxx>
- To: <argyllcms@xxxxxxxxxxxxx>
- Date: Mon, 8 Jun 2020 21:30:58 +0200
file, applies the given profile with _absolute colorimetric_ rendering
Profcheck basically takes the device values (RGB, CMYK) from the .ti3
intent in order to convert these device values to XYZ (or CIELAB),
reference
So this is the reason why I do not see the exact values from the
changedtable in the output from profcheck, because the rendering intent has
these values?
The numbers labeled with "should be" in the profcheck output ARE the
measured colors from the .ti3 file (if necessary just converted from XYZ to
CIELAB, but not mangled otherwise). Ideally, the colors predicted by the
profile (i.e. the numbers after "->") should be the same ones, but in
practice they deviate more or less due to limitations of the profiling
process and imperfections of the measurement data.
This brings up a longstanding question I have. How comes the renderingfrom
intent into play here? I always thought, the intent is used if one goes
a large colour space to a smaller one. Since XYZ / Lab cover allpotentially
possible colours, there are by definition no out of gamut values. So whatis
the role of the rendering intent here? And if so, why the absolute
colorimetric intent?
The measured XYZ in the .ti3 file are absolute colors, therefore profcheck
applies the profile with absolute colorimetric intent as well, in oder that
the compared colors are both absolute ones. Just in order to compare apples
to apples, and not apples to pears.
Regards,
Gerhard
--- End Message ---