Gamut Mapping Virtual Working Group

Document Workspace

Matthias Scharfenberg & Carol Payne - Working Group Co-Chairs
Alex Forsythe - ACES Technical Lead - email
Steve Tobenkin - ACES Adoption/Comms Lead - email
ACES Gamut Mapping VWG Home: ACESCentral Gamut Mapping VWG 
Workspace Home:  https://aces.mp/VWG_HOME
 

Problem

Users of ACES are experiencing problems with clipping of colors and the resulting artifacts (loss of texture, intensification of color fringes). This clipping occurs at two stages in the pipeline.
  • Conversion from camera raw RGB or from the manufacturer’s encoding space into ACES AP0
  • Conversion from ACES AP0 into the working color space ACES AP1

Scope

The scope of work for the working group is as follows:
  • Propose transforms between color spaces that avoid or reduce color clipping. Solutions for this may include:
  • Proposing a suitable color encoding space for digital motion-picture cameras.
  • Proposing a suitable working color space.
  • Propose a suitable gamut mapping/compression algorithm that performs well with wide gamut, high dynamic range, scene referred content that is robust and invertible.

Anticipated Deliverable(s)

  • Documentation detailing the group’s research and findings around gamut recommendations, based on real-world and CG content.
  • New proposed gamut standards (if changing)
  • New recommendation for a gamut mapping algorithm (if applicable)

Documents

Gamut Mapping Image Submissions

Upload any image files that you think would be useful for this group to have access to for testing and development of gamut mapping solutions.


Access/view the files: Gamut Mapping Image Submissions
Test images debayered to AP0 EXRS here

Gamut Mapping Algorithm WIPs

A working, living space to try and keep all relevant info/data/links for WIP algorithm work, as ACES Central can be hard to track.

Jupyter Notebook (thanks, @Thomas M!) containing the work by Matthias, Jed, and Thomas:
Jed Smith Work:
  • Simple, fast, functional, invertible. Contains only “simple” Reinhard distance compression method
  • Contains 5 different compression function methods: log, reinhard, exp, arctan, tanh
  • . Here is a comparison plotting the difference of the curve shoulder with a threshold at 0.7 and the y=1 intersect at 1.5. In the user interface these options are sorted by how aggressive the curve is starting with the lowest. 
  • log - Natural logarithm
  • reinhard - simple Reinhard style compression curve
  • exp - Natural exponent compression curve
  • atan - Arc tangent compression curve. Has C2 continuity (that is, the 2nd derivative of the curve is smooth
  • tanh - Hyperbolic tangent compression curve. Has C2 continuity. Very aggressive slope, has issues with inverse transform the farther the max distance limit is set.