I have a few ACES questions I need to answer for an up and coming project. I’ve been tasked with building some very simple looks for our show.
If I set up a managed ACES 1.3 Resolve project (Colour Science: ACEScct, Version: 1.3, IDT: ARRI LogC3, ODT: Rec709, Process Node Luts: AP1) and stick a test clip on a timeline and add some very simple CDL adjustments, can I then export those adjustments into a cube and use that to a) apply our ‘LMT’ look at the timeline level in Resolve to apply said look across an entire camera roll and B) apply the cube post CDL in a ACES managed LiveGrade project.
How would I go about exporting a LUT that encompasses the 709 output also for on set monitoring? Would I build an unmanaged Resolve project and then on three separate nodes:
ACES Transform: ARRI LogC3 - cct
CDL Valves from my ACES managed project
ACES Transform: cct - Rec709
Export as LUT
I notice there is no ‘ACES’ option (presume that would be AP0) in Resolve ACES Transform. Otherwise I would have suggested Log - AP0, AP0 -AP1 before the CDL, but maybe it isn’t needed.
I think would be relatively easy to just perform some tests to verify your questions. I’d say have a go at it if you have the time :).
But if memory serves me right, then:
Yes in Resolve creating a LUT takes only the nodes from the clip and group, not the timeline or parts of color management. If you’d re-insert that LUT into the same stage of image processing you’ll get the same result.
In theory yes. But I’m not exactly sure which limitations to consider there. You may need to check which cube resolution is supported and I’m also not sure if video or full levels are required. Perhaps this depends on the camera/monitor, it’s not my field of expertise.
The extra step to AP0/Linear is not needed as the spaces are already defined to go to AP0/Linear. As to the ACES Transform in Resolve choosing ‘No Transform’ means AP0/Linear. Makes sense but is a little ambiguous. Not sure why they aren’t calling it ‘ACES 2065-1’. Similarly in RCM ‘ACES 2065-1’ is called ‘ACES’…
One important caveat to add to the thread is that since Resolve 17 (if I’m not mistaken) some of the grading tools have become colorspace aware. This means that if you would switch the project settings from ACES to DaVinci YRGB, the actual working colorspace of Resolve will change and thus the outcome of the grading nodes might also change. Therefore, it’s always recommended to make your LUT in a two pronged approach:
Export a LUT from your creative grades when still in ACES mode. The result of this will be a LUT that expects ACEScct as input values and will also output ACEScct values, only altering your creative intent.
Bring that LUT into a DaVinci YRGB project and - as you said in the original post - put that in a ACES conversion sandwich that goes: camera colorspace to ACES cct - LUT - ACES cct to Rec709 (or whatever your viewing environment on set is). Export a LUT of this and that is suitable for standalone use when you want to convert camera space to Rec709 with your look.
What you suggest with using the result of step 1 as an ‘LMT’ to apply to entire camera rolls, or to be used as an LMT in LiveGrade is both very much correct. On top of that, this LUT is also suitable to provide to your VFX vendors. When they apply this LUT in Nuke or Fusion in an ACES setup (for viewing purposes only), they will see the same image as was seen on-set and in the dailies/editorial.
You mentioned just applying a CDL correction for the LUT. You could perform (almost) any primary correction that is not spatial or temporal in nature and put that in a LUT. For LUT creation you don’t have to limit yourself to CDL values.
Always check if the final LUT you created still matches your original grade, as it is easy to accidentally insert a grading operation that can not be translated to a LUT. By verifying the LUT to the grade as a last step you can rule this out.