HPA Tech Retreat: Academy Color Encoding System Updates

Under the aegis of the Academy of Motion Picture Arts and Sciences, hundreds of motion picture and TV technologists created ACES (Academy Color Encoding System), a color management system to enable color decisions to be successfully retained throughout the workflow. Since ACES debuted in 2014, the system has achieved SMPTE standardization and continues to evolve, under the leadership of chair Annie Chang and vice chairs Rod Bogart and Joachim “JZ” Zell. Chang listed some recent updates found in ACES 1.2.

Chang noted that ACES 1.2 includes “community-driven revisions to the CLF (Common LUT format) spec and ACES Metadata File (AMF, formerly ACESclip) spec.” She also enumerated practical problems with image matching (non-ACES related), including “different RAW settings; comparison method (rendered TIFFs vs. Quicktime files) and color management issues outside of the ACES pipeline; different framing; and implementation details (such as GPU vs. LUT box).

With regard to AMF, Chang noted that it is “a snapshot of the creative intent.” “It also eliminates or reduces color ambiguities in the pipeline,” she said. But, she added, how do you embed AMF into the existing workflow? The AMF Implementation Virtual Working Group (VWG) is tackling this and other problems by defining test vectors (success and failed); specifying use with EDL, ALE, ADSM; and creating test images.

“We ended up with an automated testing environment and have started using that to test our applications,” she said. “By implementing AMF, we are closing the color communication loop.”

Autodesk’s Doug Walker, chair of the CLF Implementation VWG, noted the scenario that led to this working group’s formation. “The common LUT may not open in the software, and that’s a moment of terror for the artist who might have to talk to their color scientist and find themselves volunteering for a live grading session,” he said. The Common LUT format is able to have a “super set” of multiple LUT formats, such as a 3D LUT with a 1D LUT.

“The idea is that CLF is a set of building blocks to represent what’s in any of the commonly used LUT files out there,” Walker explained. “They’re like Lego bricks that can be stacked together, with no limit on the length and in whatever order you want.”

ACES 2.0 is already in the works, with Chang reporting the Gamut Architecture and IDT Implementation groups are already underway. Netflix’s Carol Payne, co-chair of the Gamut Study VWG with ILM’s Matthias Scharfenberg, reported that this committee had its second meeting at the HPA Tech Retreat.

“This group will deal with methods to improve gamut colors,” Payne said. “We’ll be investigating gamut mapping and scene-referred light.” She encouraged interested parties to join the meetings, which are attended by “people from all over the globe.”

“It’s a tough problem to solve so we need more minds to participate,” she added. “Netflix believes that color management is crucial to achieving high image quality, authenticity and longevity as well as key to scaling production globally and moving workflows to greater efficiency and elasticity. ACES is the only thing like it.”