Issues regarding InvODT.Academy.P3DCI_D65sim_48nits.a1.1 in DaVinci Resolve
Stockholm based company Filmlance wants to be able to:
• initially perform an HDR-TV grade, via ODT.Academy.Rec2020_1000nits_15nits_ST2084.a1.1, in front of a monitor with the calibrated white point 0.3127 x and 0.329 y (6 500 Kelvin);
• subsequently perform a D-Cinema grade, via ODT.Academy.P3DCI_D65sim_48nits.a1.1, in front of a Christie Projector with a calibrated white point according to SMPTE RP 431-2 and SMPTE ST 431-1, i.e. 0.314 x and 0.351 y (near 6 300 Kelvin);
• finally perform the D-Cinema mastering via ODT.Academy.DCDM_P3D65limited.a1.1.
Please, try to answer the following two questions!
• Should Filmlance trust DaVinci Resolve’s “ACES Output Device Transform” named “P3-DCI (D65 sim.)” although red (unexpectedly) is offset as high as blue?
• Why does not DaVinci Resolve’s “ACES Input Transform” also named “P3-DCI (D65 sim.)” perform a perfect inverse? Note: The inverse “P3-DCI (D60 sim.)” seems to work, but not the inverse “P3-DCI (D65 sim.)".
The test to be replicated, please:
• Use a shot with a Grey Card, 18% reflectance, e.g. ARRI’s frame “Isabella.112782.ari” downloadable at https://www.arri.com/resource/blob/67438/a87188ffbb425d3f42d013793f767b93/2018-acesreferenceimages-data.zip
• Use Projects Settings / Color Management / Color Science: ACEScct; ACES version: ACES 1.1; ACES Input Device Transform: Alexa; ACES Output Device Transform: No Output Transform (i.e. ACES 2065-1 AP0 straight out).
• Use a Window Node to lower the gain towards black regarding everything else in the frame than the Grey Card area.
• Use the Primary Offset Node to balance Red and Blue to the Histogram position of Green:
• Change “ACES Output Device Transform” from “No Output Transform” to “P3-DCI (D60 sim.)”! The below behaviour is hopefully correct as the red channel has become higher than blue and green to compensate for the greener DCI white (as described in the code at https://github.com/ampas/aces-dev/blob/master/transforms/ctl/odt/p3/ODT.Academy.P3DCI_D60sim_48nits.ctl):
• Deliver a video. Import that video and, to that specific Clip, enable “ACES Input Transform” “P3-DCI (D60 sim.)”, i.e. the inverse! Put the Project Setting “ACES Output Device Transform” into “No Output Transform” and one seems successfully back. DaVinci Resolve’s Inverse-version regarding D60 simulation seems to work:
Now the same test regarding D65 simulation, that is critical to Filmlance:
• Change “ACES Output Device Transform” from “No Output Transform” to “P3-DCI (D65 sim.)”! The below behaviour is hopefully correct as the blue channel has become higher than red and green to compensate for the greener DCI white (as described in the code at https://github.com/ampas/aces-dev/blob/master/transforms/ctl/odt/p3/ODT.Academy.P3DCI_D65sim_48nits.ctl). However, the red channel is unexpectedly offset, nearly as high as the expected blue – is that correct?
• Deliver a video. Import that video and, to that specific Clip, enable “ACES Input Transform” “P3-DCI (D65 sim.)”, i.e. the inverse! Put the Project Setting “ACES Output Device Transform” into “No Output Transform” and one has an unexpected problem. DaVinci Resolve’s Inverse-version regarding D65 simulation seems to be wrong:
Thanks for all your help, in advance!
Stockholm, January 20, 2020