On Jun 17, 2017, at 06:14 000AM, Carsten Kurz via DCPomatic <dcpomatic@carlh.net> wrote:

Another ‚indicator‘ - I took your rec709.TIFF, fed it through OpenDCP to make an XYZ-transformed J2C from it. Then converted to TIFF (with no color transform). That is, to see how a ‚proper‘ XYZ-TIFF of that content should look like, compared to the version that the post house delivered. See attached picture (clockrec709_xyz.tiff)


This XYZ-TIFF converted from the rec709.TIFF looks very different from the post house version. Of course, I also fed this XYZ-TIFF through DCP-o-matic, applied ‚no color conversion‘ - and the result in the DCP looks identical to the rec709 version (aside from some minor gamma changes, but that shouldn’t bother us for now (rec709, 16Bit/8Bit, etc.). I also attached three snapshots from the same DCP, converted from all these sources with DOM:

- first image (DCP_snap_TIFF_XYZ_org.png) is what you know - the original posthouse XYZ-TIFF converted to DCP with ‚none‘ - greenish clock
- second image (DCP_snap_TIFF_rec709_org.png) is your original rec709.TIFF, converted to DCP with the rec709/sRGB conversion - white clock
- third image (DCP_snap_TIFF_rec709_XYZ.png) is the rec709.TIFF, converted to XYZ->J2C->XYZ-TIFF, and then again converted to DCP, again with ‚none‘ - white clock. 

You see that this XYZ-TIFF I created from the rec709.TIFF, with no color conversion applied in DOM now matches the rec709 and thus your preferred look very closely.

Now, I am not a color scientist, but to me this seems to prove that whatever the post house gave you was not made to transfer 1:1 into a DCI J2C/MXF…

So I’d get back to them and try to solve it with them.

- Carsten

<clockrec709_xyz.tiff><DCP_snap_TIFF_XYZ_org.png>

<DCP_snap_TIFF_rec709_org.png><DCP_snap_TIFF_rec709_XYZ.png>

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