Compositing in ACES with a LUT getting different results in different apps

[justini]

So I've been experimenting with compositing workflows using LUTs in ACES colour space. In After Effects, Davinci Resolve and the VFB I'm getting very slightly different results when the LUT is applied. I'm assuming the VFB version is "correct" but that leads me to question why are there difference and what needs to be done in each application to get a consistent result??

My set up in each application is described as follows and respective outputs are attached. The differences are subtle but definitely noticable.

In Resolve:
I'm working in ACEScc colour science, with ACEScg as the input transform and Rec.709 as the output transform.
In the "Colour" module I add 3 nodes:

• Node 1 - Transform the output color space and gamma to Rec.709.
• Node 2 - LUT
• Node 3 - Transform the input color space and gamma to Rec.709

In After Effects:
Project settings are set to 32bit colour depth, Rec.709 as the Working Space, and Linearize working space checked.
Above the footage I add 3 adjustment layers

• Layer 1 - LUT
• Layer 2 - OpenColorOCIO set to ACEScg as in teh input and Rec.709 as output
• Layer 3 - Color Profile Converter with Input and Output set to Rec.709 and "Linearize Output Profile" checked

VFB:
OCIO checked under the "Display Correction"
Input Colorspace set to ACEScg
Display Device set to ACES
View Transform set to Rec.709
Lookup Table added with "Convert to sRGB first" unchecked.

[Muhammed_Hamed]

The order of applying the LUT matters, it needs to be linear and prior to the view transform
I believe the results should match between all 3, upload me the exr and I will give this a try

Best
Muhammed

[piotrus3333]

not sure if that is the case here but vfb’s lookup table layer can only access 0-1 range and output is clipped to 1.
so lets say ‘linear to cineon log’ lut will work in Resolve/Fusion and not in VRay.

[piotrus3333]

you might find this helpful. LUTs you use go after attached LUT. like grading log basically.

Making ACES a bit more flexible in VFB - Chaos Forums

[justini]

Thanks for this. An explanation would be helpful. Not sure what your video is demonstrating exactly or how it's helpful.

[piotrus3333]

it is a workaround for ACEScg workflow that allows use of LUTs in VFB.

[justini]

Thanks. VFB is nice too but I don't tend to do final grades in it. My main question is how to apply LUTs correctly in compositing apps using ACES colour space.

[piotrus3333]

apply the LUT in the space it is intended for. ACEScc and cct are designed for grading.

[Muhammed_Hamed]

Thanks. VFB is nice too but I don't tend to do final grades in it. My main question is how to apply LUTs correctly in compositing apps using ACES colour space.

Check out my video here

Best,
Muhammed