XYZ source file to DCP is shifting color

[Nasty]

I have a Prores 4444 XQ I'm using as my source file that has properly been converted to XYZ before rendering. When I add my XYZ Prores into DCP-o-matic and set "Colour" to None, color is changing in the DCP when checked against the source. The DCP's color is shifting to yellow/green. Any suggestions on what I'm doing wrong?

[Carsten]

There could be many possible issues with your XYZ conversion - limited vs. full color range, gamma issues, etc. When disabling color conversion, DCP-o-matic takes no responsibility for your source color space conversion and assumes it to be X'Y'Z' (inverse 2.6 gamma) full range at DCI whitepoint.

You are not following a standard procedure when creating your master file.

[carl]

Hi,

When you compare the DCP against the source, are you looking at the DCP in the DCP-o-matic player, or some other way?

How did you create the XYZ Prores?

Is it possible to prepare a short sample clip that demonstrates the problem, and send it to me? carl@dcpomatic.com

[Nasty]

My original source file is a P3D65 Prores 4444 XQ. I am converting to XYZ in Resolve and can confirm that the conversion is accurately converting from P3D65 to XYZ.

If I render the P3D65 file converted to XYZ from Resolve as a 16bit TIFF sequence DCDM and input that source into DCP-o-matric, set Colour to None and create a DCP, color is correct.

But if I render that same timeline as an XYZ Prores 4444 XQ and set Colour to None, the DCP color is shifted. I don't think its a range issue as there is no shift in brightness.

If DCP-o-matic is taking no responsibility for my source color space conversion when set to None, shouldn't DCP color match the source regardless?

I'm comparing the DCP to the source in Resolve with my timeline/output color space set to Rec.709 Gamma 2.4. Both the DCP and Prores source are converted to Rec.709 Gamma 2.4 under the same conversion.

I will go ahead and send a sample, thanks for your help!

[IoannisSyrogiannis]

My original source file is a P3D65 Prores 4444 XQ. I am converting to XYZ in Resolve[...]

If I render the P3D65 file converted to XYZ from Resolve as a 16bit TIFF sequence DCDM[...], color is correct.
[...]

I will not pretend that I know the answer, but doesn't that seem like the color difference between the two cases is (also) affected by that last four bits of alpha channel on 4:4:4:4 and that would not be present as an extra channel on the 16bit TIFF sequence DCDM?

I will second the the point Carsten made about gamma and DCI white point. If no brightness change appears, it would seem to me more probable that in the first case the white point remains on P3D65. If I am not mistaken, P3-D65 white point is x=0.3127 and y=0.3290, while DCI-P3 is x=0.314 and y=0.351. That means a shift that would have to take place on it (white point) towards the top and the right of the CIE chromaticity diagram, wouldn't that be the case?

Edit:
To give some substance in the difference, here is the two white points. The triangle one is the DCI one, the spade one is the D65.

CIE1931chromaticitydiagram031403510312703290.png

[carl]

This should be fixed in 2.18.19 - let me know if not!