DPX and CG composite workflow

Discussions - Using ACES VFX
1

We have a project composite CG+live action footage. CG elements EXR render from Vray (in acesCG). The live footage DPX is export from resolve (not aces). How to setup a workflow correctly in Nuke? Thanks

2

Hi Luludohk,

the most basic setup would be set Nuke to ACES, set the viewer right for your display and load the live action plates with the right camera IDT and start comping.

After the comp you may want to export EXR (ACES) files or go back to the camera space and write out again DPX files. Just be aware that the DPX files will clip high values whereas they will be kept intact in an EXR file.

I hope this helps as a first step.

Daniel

3

@luludohk

Agree with everything Daniel said. Additionally, you may find this video helpful

Working with DPX in ACES

4

Thank you for the reply.
Just asking DI company. They using “Rec709 Gamma 2.4” to Output the DPX.

This is my workflow:

  1. Nuke set to ACES
  2. Read node to RAW
  3. using OCIO colorSpace “in to Unitily Rec709 Camera and out to ACEScg”
  4. Some composite work
  5. Before Write node using OCIO coloSpace “in to ACEScg and out to Unitily Rec709 Camera”
  6. write node set to RAW (DPX format)

Is it correct?

5

DPX should be in the native log format of the camera it was shot on. So you need to ask what the camera was that it was shot with, and ideally get a sample RAW file to check. Whatever camera color space the DPX is in, that is what you should set your read node to (and your write node). Don’t use OCIO colorSpace nodes, just set the read and write nodes correctly. If for example the DPX is from an ARRI camera you would set the read node’s input transform to ARRI Log-C. This will convert from ARRI Log-C into ACEScg which is the working color space in Nuke. You likewise would set the write node’s output transform to ARRI Log-C which will convert from ACEScg to ARRI Log-C.

so

1. Nuke set to ACES
2. Read node to camera color space (Log-C for example for an ARRI)
3. Some composite work
4. write node set same as read (DPX format)

Rec709 Gamma 2.4 is not a log format, it is a display type. The DI facility is likely viewing on a Rec709 Gamma 2.4 monitor and working non-color managed. This however is not the color space that the DPX is in.

6

Thank Derek. It shot from ARRI mini. Can i know which ARRI Log-C should choose?

7

I believe there is just one in the ACES ocio config.

8

The Nuke Read node is always automatically converting from the colourspace you set to the working space (ACEScg) and the other way around for the Write node. There should be no need to set the nodes to “raw”.