Linear to ACES

Sadly I’m on a project where one of the VFX shops is imposing deliver their job in Linear(nuke I assume) other parts of the pipeline are in ACES, but I’m not sure how to go from linear to ACES. Any tip,workaround or life saving IDT?

Hi Fabian,

The ACES working space for CG, i.e. ACEScg, is scene-referred thus linear and would be appropriate for comping in Nuke. Note that inter-exchange should be done with ACES2065-1 though which is also scene-referred. Are you able to shed a bit more light on where you are sitting in the chain and which working space you are currently using?

Cheers,

Thomas

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I usually send the VFX plates in AP0. Would you consider this a bad thing? My reasoning behind this is that plates should be in the biggest space possible in order to make sure that all colors coming fomr the camera are included. And usually VFX houses know that they need to convert from 0 scene reffred to 1 scene refered ( ACEScg).

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Hi Fabian. Are you using Resolve?

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That is perfect, it is the RGB colourspace they should be delivered in as per SMPTE ST2065-4 and the reference implementation: https://github.com/ampas/aces_container/blob/master/aces_attributestructs.cpp#L218, note that the EXR files should have the acesImageContainerFlag attribute set.

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Hi guys thanks for the answers. I Answered yesterday but not sure why it didnt arrive. I do use Resolve and I do send the plates in AP0, with the other vfx from this project there is no problem, but one vfx shot recieved the footage directly from the shooting and now they dont want work in ACES, they say they will send the clip on linear. So im not sure how to deal with it since there is no IDT that transform from linear(probably rec709 linear not sure yet).

‘linear’ is only a description about the greyscale encoding, not about the colors (colors will be defined by a gamut). So ACES can also be ‘linear’, just identical to what you call ‘linear’. So you only need to deal with the gamut of this data, as the data already is the ‘linear’ you need.
If they use the ‘linear’ colorspace in Nuke etc., they just leave the colors as they are, so probably the native gamut of the footage from the camera. So you need to know how this footage was shot. For example if it was shot with an ARRI camera, it probably is in Alexa Wide Gamut. If it was shot with a RED, there are different possible gamuts. Without knowing the original gamut, you can’t do a proper conversion.
So maybe you could get a frame from the original footage (the input stuff of the other VFX shop, not their output!) and have a look into the metadata. This should give you a hint, how this footage was shot and which gamut it may have.
After you know this, you can just use the colorspaces in the ACES configs that have a ‘linear’ in their name. For example to convert an ARRI footage you would choose “Input - ARRI - Linear - ALEXA Wide Gamut” as input colorspace and “ACES - ACES2065-1” as output space to convert to linear AP0. Same goes for all the RED colorspaces.

Hi Fabian,

What is the source file? Alexa, Red, Sony?

In resolve just add a colorspace conversion ofx and swicth from source gamma (logc, log3g10, slog3) to Linear and leave the gamut as is.

From there just export an EXR and you’re good to go!

Cheers!

Thanks @Thomas_Mansencal!