Does ODT.Academy.DCDM_P3D65limited.a1.1.0 include the identical (pre)processing of R, G and B (before conversion to XYZ) as found in ODT.Academy.P3DCI_D65sim_48nits.a1.1.0 regarding “compensation for different white point being darker” and “roll off of highlights to avoid need for as much scaling” described in the code-text at https://github.com/ampas/aces-dev/blob/master/transforms/ctl/odt/p3/ODT.Academy.P3DCI_D65sim_48nits.ctl?
The colourist’s projector is calibrated with X’Y’Z’ based test-patches according to SMPTE RP 431-2.
In the normative Table A.4: The patch called “White-2” (DCI’s D63-based projector calibration), with 12-bit integer X’Y’Z’ values 3794/3960/3890, is possible to create mathematically based on initial R’G’B’ 4095/4095/4095.
However, patch “White-1” (D65) and patch “White-3” (D55, legacy Xenon projector lamps) seems “synthetic/wrong” as they cannot be created mathematically based on initial R’G’B’ code values in the 0-4095 range – e.g. the D65-patch would need impossible 4097/3896/4179 as initial R’G’B’ in order to eventually display 48 nits in luminance.
This issue is described in the code-text at https://github.com/ampas/aces-dev/blob/master/transforms/ctl/odt/p3/ODT.Academy.P3DCI_D65sim_48nits.ctl.
The issue does not seem to be described in the code-text at https://github.com/ampas/aces-dev/blob/master/transforms/ctl/odt/dcdm/ODT.Academy.DCDM_P3D65limited.ctl.
Hence, there is a worry that the colourist will enjoy the “roll off” in his viewing-ODT (to avoid the viewing of clipped B’ causing nuance shift in the highlights) – while audience in cinemas may experience clipped B’ feeding the projector lamp, giving an overall nuance shift in the highlights, via the DCDM-based DCP.
(Note: The mastering of the DCDM, and the packaging of the DCP, is not performed by the colourist. Mastering and QC is performed subsequently by another colleague in another viewing environment).
Stockholm, November 18, 2020