Profcheck basically takes the device values (RGB, CMYK) from the .ti3 file, applies the given profile
with _absolute colorimetric_ rendering intent in order to convert these device values to XYZ (or
CIELAB), and compares the result of the conversion with the measured XYZ/CIELAB values in the .ti3
file. The values after "->" are the colors predicted by the profile, and the "should
be" values are just the measured colors from the .ti3 file. Due to imperfections/limitations of
the profile and noise in the measured data, they are not expected to agree exactly.
Btw, the "measured XYZ/CIELAB values" may be actually calculated on the fly
from spectral measurement data in the .ti3 file (e.g. when a custom illuminant or custom
observer are specified).
Regards,
Gerhard
Am 06.06.20 um 10:06 schrieb Hermann-Josef Röser:
Good morning,
sorry, but I want to ask again, having read the documentation about
profcheck again. There it is stated that "The absolute forward table in the
profile is used to create PCS values from the sample points, and the
profiles PCS value then compared to the PCS values of the measured sample
points." I interpreted these as the columns behind "->" and behind "should
be".
Obviously I do not understand correctly what PCS is. I had thought that PCS
is the XYZ or the Lab space. But when I look at the output of profcheck,
this does not seem to be the case. So let me re-formulate my question here:
What is the difference between PCS and XYZ / Lab?
Hermann-Josef
-----Ursprüngliche Nachricht-----
Von: Hermann-Josef Röser [mailto:posts@xxxxxxxxxxxxxxxxxxxxxxxxx]
Gesendet: Montag, 1. Juni 2020 17:11
An: 'argyllcms@xxxxxxxxxxxxx'
Betreff: Question about log-output from profcheck
Hello,
looking at the log-file created by profcheck, I would like to ask for the
meaning of the individual columns:
[0.169388] A01: 0.23964410 0.16430230 0.15892750 -> 16.409908 8.574043
2.164033 should be 16.454333 8.492457 2.331527
I would have expected that the values behind "->" and behind "should be"
correspond to the Lab-values. However, the "should be" values differ from
these, e.g. for the patch A1 the reference table gives 14.85 8.55
2.41.
Where does this difference come from?
