Verification Calculation Bugs?

[Ping]

When I use the Verification function of DisplayCAL, Sometimes I find obvious errors when calculating the color difference between the Measured whitepoint and the Assumed target whitepoint

such as the target D65 light source xy 0.3127 0.329 (XYZ 95.05 100 108.91), CCT 6504K,
the actual measured xy 0.3155 0.3313 (XYZ 95.23 100 106.62), CCT 6339K,
Measurement Report shows ΔE*00=0.69, but this is obviously wrong;
after correct calculation, ΔE*00 should be 1.693816

Is there any solution for this problem?
Thank you~

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[Patrick1978]

You’re looking at the wrong thing.  Measured vs. assumed target whitepoint is what was measured vs a made up number close to the actual white point in the profile. What you should be looking at is the measured vs display profile whitepoint which shows as 1.44

Second the numbers you have in the converter don’t match up with what I’m getting when I do the conversion from xy to Lab so  that’s the likely reason for your discrepancy.

Using that site to convert xyY to Lab with ref white set to d65 and Y at 1.0 then using the color difference calculator gives me almost the same results as your measurement report.

profile      xy 0.3127 0.329  Lab 100.0000 -0.0025 -0.0139
mesured xy 0.3155 0.3313 Lab 100.0000  0.3223 1.4013
assumed xy 0.3161 0.3325 Lab 100.0000 0.0362 1.9780

So I get 0.688816 for the measured vs. assumed target whitepoint
and 1.448910 for measured vs display profile whitepoint

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[Ping]

Oh you are right, I didn’t notice the difference between “Measured whitepoint”, “assumed target whitepoint” and “Display profile whitepoint”.

Thank you for your answer

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