[argyllcms] FWA overcompensation bug in spec2cie
- From: Alexey Gribunin <Gribunin@xxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Wed, 14 Jul 2010 14:16:09 +0400
Hello Graeme!
It seems to me that I found bug in spec2cie.
It's a FWA overcompensation of LAB (and XYZ) values.
I'm running the following command on Test.ti3 measurements, which
contains FWA (paper Lab values are 95.71 -0.48 -2.91):
spec2cie.exe -i ref/D50_0.0.sp -f -o 1931_2 Test.ti3 Test_UVCut.ti3
#command 1
In Test_UVCut.ti3 I have both spectral and LAB values. I think, they
should match but they don't!
Spectral values seems to be FWA compensated correctly. After converting
spectrals to Lab with the following command:
spec2cie.exe -i D50 -o 1931_2 -n Test_UVCut.ti3 Test_UVCut_CIE.ti3
#command 2
I got paper Lab values 95.61 -1.33 0.24.
The same correct result I got by converting spectral values from
Test_UVCut.ti3 to Lab in XRite MeasureTool (it's little bit tricky to
extract spectral values from TI3 but it works).
But LAB values which I got in Test_UVCut.ti3 (#command 1) are wrong!
Paper Lab values are 95.61 -2.37 2.64. Overcompensation!
It seems to me that #command 1 makes FWA compensation twice. First time
it makes compensation of spectral values, and the second time it makes
compensation when converting compensated spectral values to Lab.
Best regards,
Alexey Gribunin,
UNIT Color Technologies,
Moscow, Russia.
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