Any reason to use ACES when onlining material with a burned-in LUT?

Discussions - Using ACES Post (DI, Edit, Mastering)
1

Hi, folks.

I’ll soon be onlining an indie feature which was captured in ProRes 4444 with a REC-709 LUT burned into the footage. Is it possible to use an ACES workflow with source material which is not either RAW or in a Log gamma? If it is possible, is there any added value to working in ACES in this case?

I’ll be working in Resolve 15.

Thanks for your time.

Keith Putnam

2

Presumably the only benefit might be in making a 2065-1 IMF master file at the end.

3

Hi Keith.
Technically, you can use an inverse Output Transform as the Input Transform for your Rec.709 footage to pull it “back” into ACES color management. Whether this enhances or not your workflow is another matter.

In fact, is it correct to say that your original footage was recorded with a burnt-in Rec.709 LUT ?

If that is it, and since it is now stored in a narrow-gamut, display-referred color space, you won’t have any advantage in gaining color depth out of your source footage by converting it into ACES2065-1
But in case you are using multiple cameras and/or multiple output deliveries, there may still be some advantage in using an ACES workflow.

4

Thank you, Walter. That’s pretty much what I expected. I’ll create the final master in REC709, with perhaps a REC709 -> P3 transform for a separate projection master.

5

Keith,
what I was really implying in my previous comment is that working in Rec.709 is not at all a good choice. That may be your target space for rendering the deliveries for things like SDR TV or web.

But I understand that, since all camera footage has been baked in with a Rec.709 LUT, this might be too late to tell.

I strongly advise you against using Rec.709 (as well as either output-referred and SDR color-spaces) as a working/grading space. Switching to a larger space afterwards (like ACES2065, or P3 as you are suggesting now) will not restore color definition, latitude, gamut back.

6

Your surmise is correct, that all the footage has a LUT baked in (not a manufacturer default REC709 LUT, but a REC709-legal LUT all the same). This was a deliberate choice made during production as one can never be sure a microbudget feature will ultimately get any kind of color grade.

So far I’ve been pretty impressed with how much I can push ProRes 4444 around even with a LUT baked in; I’m used to grading over RAW / LogC.