Hello, I don’t know if this is the place to post a topic to ask for a hand (thank you for your patience).
I have to set up a nuke workflow with the specs of a lab but I can’t find my way around.
Here is the production context for VFX:
source: Arri Alexa LogC4 ARRI Wide Gamut 4 (the lab indicates to provide in ACES Linear AP0 2065-1, but the meta data clearly indicates that the rush exr is in LogC4 ARRI Wide Gamut 4)
and the lab notes this to work;
ARRI Alexa, Colour order of operations for Rec.709 Quicktimes:
ACES 2065-1 AP0 => Nuke: OCIO to LogC4 ARRI Wide Gamut 4 => CDL Grade > Rec709
Show LUT (full range) Scale to Rec709 legal video range (16-235) 2.4Gamma
(this whole part is a mess ! I precise i’m a junior)
I tested by putting my project settings in aces2065, in aces cct or acescg but impossible to make an export that looks like the lab reference video.
I feel like I’m at a dead end, so someone can guide me?
Hello @TooDee ,
I switched AriLogC4 to Linear Arri Wide Gamut 4 and now i’m close to match the result; it’s much better but It seems there is a little shift somewhere (gamma and color) to match the lab reference.
The plates you receiving are in ACES2065-1 according to the spec so you need to convert these to LogCV4 apply the provided cdl and then apply the supplied display lut using the file transform nodes. This is a pretty standard ACES hybrid workflow.
Your config needs to be an ACES OCIO config so exrs are treated as ACES2065-1 currently I see the read node set as Alexa Wide Gamut v4 this is not correct they are giving you ACES 2065-1 encoded files
The read node should be set to ACES 2065-1 which will put the colour into ACES cg working colourspace of Nuke. Use a colorspace node to convert from ACEScg to Alexa LogCV4 then apply the cdl and the provided display lut. It should match the reference then.
Hello, thank you for your valuable information; I was finally able to find the solution that corresponds to what you describe!
it was necessary to put the project in Acescg; the read in Aces2065 add an ocio look transform from Acescg to Arri Logc4; then cdl and lut.
So we have a perfect match with the ref edit of the lab!!
I’m running into this same issue, but in Resolve 18.1. I’ve been asking around everyone I know seems to be struggling to figure this out. The main stumbling block seems to be going from ACES to LogC4 because LogC4 is listed as an input and not selectable as an output in the CST or ACES nodes. Any help would be greatly appreciated.
It’s a good point. ARRI LogC4 has been added to the IDTs in the aces-dev GitHub repo, but is not included in the CSCs. I have just opened a PR to add it to the CSCs.
It won’t happen immediately, but if my PR is accepted, ACES implementations such as Resolve should follow on, and add it to its list of CSCs.
Hello everyone, I’m not sure If this issue is solved, but if someone needs it, I encountered the same issue with the LogC4/Arri-Linear v4 for a project.
And ended up getting the 1dluts and proper matrix conversions to go in and out from an Aces workflow.
cheers
