I have a color question for you.
I 'm in an ACES project where everything works very well as everything comes from the same shoot.
Now, on a shot from the inside of a building, I’m asked to replace an outside sky because it’s too white and flat.
My problem is that, in the original rush, I have luma values in the sky that go up around 15 or 20. The light bleed on the window surroudings walls (that go up to 4 or 5 sometimes).
The sky I’ll have to integrate will most likely be a stock footage, in REC709 with values always between 0 and 1.
Event if I convert that in ACES cg (with the View transform inverted trick), I will still have values between 0 and 1 so it will never match the original plate. And if I push up the exposure, I could get very high values but I’ll loose every cloud and details I would like too keep (not loose as they will still be here but it’ll still be very hard to Grade)
Is there a way to bring my Rec footage into tha ACES cg colorspace, matching the aces plate levels but keeping visual as close to Rec 709?
Sorry if it’s not clear but any help would be super good. Thx
A trick I’ve started using is to color correct your 709 material before the view transform to make it less nuclear. If you plug a 709ified version of the plate you’d like to match into the background input of a CC node, sample white values from your foreground and background, and use the Match button in the Curves tab, you can be pretty precise with how well it transforms to Aces. Or you can tough it out with manual gain adjustments, but in my experience this gets very messy very fast.
Thx, will try that. I’ve already tried to make them both ACES cct to reduce the difference as well but I still had to push very very hard on my originally Rec709 plate. Will try that anyway.
Interpret your Rec.709 as video
Use a Colour Mgmt node set to View Transform with the Invert button toggled, the Display set to Rec.709 video, the Tagged Colour Space set to ACEScg and the View Transform set to “From Rules” to match your default viewing rule in your preferences, or manually set to some other view, typically “ACES 1.0 SDR-video”.
Mabye. It’s set in a way that I can’t visually see any difference between my Rec709 plate viewd with Video View transform and its ACES version viewed with ACES view Transform. Isn’t that the way to go?
It sounds like you are doing well so far but the invert should make some bright values break out above 1 so that they fit better into your ACEScg material.
Thx. I’m doing exactly that and I have to appologize as I have values above 1.
It’s just that I get 1,2, sometimes 1,5 but I’m still so far from the 15 from ACES plate!
Your Rec709 sky used to have these high values before it was tone mapped into SDR range. Hence the mismatch.
So now you have to make them match again. In a super simple pipeline, you could do the comp after the view transform of your plate. But in most cases that’s not an option because you want to stay in ACEScg.
So that means you have to bring the sky to the rest of the party. There are two ways - one is mathematical correct, the other one is visually closer to what you expect. Neither one is perfect.
a) Bring your sky plate in with the Rec709 input transform. It will remain muted, so you’ll have to manually grade it to match.
b) Bring your sky plate in with the Rec709 view transform and invert enabled. It will do some of the ‘grade’ for you, but is not mathematically correct.
The real problem is that when that sky was saved in Rec709 it was a lossy operation in terms of the orignal tonal detail. That data is gone and not coming back. So you can pick your compromise of artistically restoring it.
Thx. I have turned my Rec plate into Aces with a View tranform and graded it heavily so it matches as well as possible. Probably not prefect result but close enough.
Was hoping there was a way to promote the clamped Rec values to something artificially wider (other than doing it by hand).
Thx
