I realized that after grading an Arri Alexa footage in aces with p3d65 out,( IDT logc to acescct - ODT ACEScct to p3d65), when I switched the ODT to p3dci , I don’t see any gamma shift. Shouldn’t be a 2.4 to 2.6 conversion?
Both P3-D65 and P3-DCI are designed for gamma 2.6, so no, you should not see any noticeable gamma shift.
Each is designed to encode the values slightly differently depending on how your projector is set up. Use the ODT for the display encoding that your projector or display is calibrated to, then the output should look the same for each if viewed on the corresponding display.
The P3-D65 is intended for a projector with P3 primaries that has been set up such that equal neutral RGB code values sent to the projector produce a chromaticity equal to that of D65 and that the peak neutral luminance is 48 nits. The assumed observer adapted white is D65, and the viewing environment is a dark surround.
The P3-DCI (D65 simulation) ODT is intended for a P3 digital cinema projector that is calibrated to a DCI white point at 48 cd/m^2. The assumed observer adapted white is D65, and the viewing environment is a dark surround.
Thanks for your reply Scott.
Then, grading in p3d65 with a 2.4gamma is impossible in aces,right? or the solution should be “grading in rec2020 p3d65 limited” ? Is there a source that I can look up for all the details of the default odt gamma values?
Shouldn’t be there a separate gamma option in Aces apart from the default gamma of the ODTs? at least for the p3d65?
No, not impossible. It is very possible.
ACES supports all sorts of customized ODTs with any combination of primaries, EOTF, white points, luminances, etc.
We provide default ODTs to the most common outputs. But the base code has parameters for all of these different attributes. However, not all software that implements ACES transforms makes the full display parameters available - they just ship the common ODTs in their menus by default. It is possible to add custom variants for non-standard display setups, such as P3D65 g2.4. What software are you working in?
Thanks Scott . I am working in Davinci Resolve.