ACES / 3ds Max Color Management

[ryan_companies]

With the color management introduced in Max 2025+ we've been trying to figure out the proper workflow to update our model libraries moving forward. Fundamentally we understand the workflow of ensuring we are in the new default color management space and updated all the VRayBitmaps to the proper color space transfer function and RGB color space parameters. What's unclear is what View Transform we should use in the VFB -- do we leave it as ACES 1.0 SDR-video or do we need to change it to un-tone-mapped? I've attached examples of what a grass model we have looks like in gamma color space, ACES SDR-video and ACES un-tone-mapped.

It appears that the un-tone-mapped version is the correct view transform? SDR-Video has a lot of extra contrast and feels off.

[hermit.crab]

Tried to answer it myself, but this thread in the Nuke subreddit explains it better. Basically, ACES 1.0 SDR-Video is meant to map out HDR (floating point above 1) values to SDR ones, essentially allowing a preview of images with a higher dynamic range. Using the Un-tone-mapped view transform, you'll preview linear 0-1 values, similar to the standard sRGB / Gamma 2.2 curves.

[ryan_companies]

Understood, that makes sense and appreciate the subreddit thread for the deep dive. I think I resolved our issue of seeing different outputs from Gamma 2.2 to ACES -- it was related to the HDRI file in the dome light. I've been using PG Skies for 95% of my lighting for years (that's what the light source is in the images above) and I think what is happening is PG Skies maps were specifically developed for Gamma 2.2 workflows, not ACES. I tried a Cosmos HDRI and the results were what I would expect, with shadow detail being brighter and not so contrasty, additionally having similar results with Sun and Sky setups.

TLDR; HDRI maps I've been using for years don't seem to be calibrated properly for ACES, nothing was actually wrong in the scene.