ACES + composite modes + exporting EXRs without an ODT + potential Resolve bug?

Discussions - Using ACES
1

Hi,

I’d like some guidance on the following problem, but before that, some context:

I work in Resolve using ACES 2.0/AP1/ACEScct on a project-settings level with the ODT set to Rec. 709. Very straight forward. I export all of my projects as EXRs (RGB half zip) without an ODT (so basically, linear).

The issue/bug (simplified here) I encounter is as follows:

  1. I place a clip on the timeline.
  2. On the color page, I add a node and change the node’s composite mode to Multiply.
  3. I disable the ODT and render out EXRs.
  4. I import the EXRs and re-enable the ODT to 709.
  5. I place the export EXRs above my original clip. The two clips don’t match.

I am pretty sure it’s a Resolve bug. Can anyone else confirm?

2

What is the purpose of the multiply?

3

I use it for a specific reason, but I don’t think that’s really important. Someone might use another type of composite mode for some other reason. I’m just trying to find out why this effect “breaks” when exporting EXRs without an ODT.

4

If you do this, it works, correct?

  1. I place a clip on the timeline.

  2. I disable the ODT and render out EXRs.

  3. I import the EXRs and re-enable the ODT to 709.

  4. I place the export EXRs above my original media. The two clips match.

    So I’m looking to identify the source of the unwanted behavior, with seems to be in your step two with the multiply. I think you would need to disable all grades before exporting.

5

Hi Derek,

Yes, I know the source of the problem is the node set to Multiply. I’d like to know why this is happening.

6

I’d start by attempting to rule out project color management. Does it occur if you manage via nodes only?

Do any code values change at all if you set an empty node to multiply?

7

Hi,

Thanks for replying. No, I cannot rule out color management because that’s how we are set up to work at our facility. We are three colorists and we all work the same – ACES color managed on a project settings level, and export our masters as EXRs sans ODT. I’ve tried node-based color-management. If I perform the Multiply operation before the IDT, then all works as it should. Unfortunately, that’s not how we work. It’s a Resolve issue.