Notice of Meeting - ACES Gamut Mapping VWG - Meeting #35 - 11/19/2020

ACES Gamut Mapping VWG Meeting #35

Thursday, November 19, 2020
9:30am - 10:30am Pacific Time (UTC-5:30pm)

Please join us for the next meeting of this virtual working group (VWG). Future meeting dates for this month include:

  • TBD

Dropbox Paper link for this group:

We will be using the same GoToMeeting url and phone numbers as in previous groups.
You may join via computer/smartphone (preferred) which will allow you to see any presentations or documents that are shared or you can join using a telephone which will be an audio only experience.

Please note that meetings are recorded and transcribed and open to the public. By participating you are agreeing to the ACESCentral Virtual Working Group Participation Guidelines

Audio + Video
Please join my meeting from your computer, tablet or smartphone.

First GoToMeeting? Let’s do a quick system check:

Audio Only
You can also dial in using your phone.
Dial the closest number to your location and then follow the prompts to enter the access code.
United States: +1 (669) 224-3319
Access Code: 241-798-885

More phone numbers
Australia: +61 2 8355 1038
Austria: +43 7 2081 5337
Belgium: +32 28 93 7002
Canada: +1 (647) 497-9379
Denmark: +45 32 72 03 69
Finland: +358 923 17 0556
France: +33 170 950 590
Germany: +49 692 5736 7300
Ireland: +353 15 360 756
Italy: +39 0 230 57 81 80
Netherlands: +31 207 941 375
New Zealand: +64 9 913 2226
Norway: +47 21 93 37 37
Spain: +34 932 75 1230
Sweden: +46 853 527 818
Switzerland: +41 225 4599 60
United Kingdom: +44 330 221 0097


  • @nick has a first version of the CTL deliverable, PR here for comment.
  • Talked a bit more through the despill issue brought up by a tester from MPC, all agreed that the benefit for compositors is being to apply at will - upstream and downstream operations will be necessary
  • Documentation:
    • Technical doc - specs, math, how it works
    • User documentation - examples, use cases, things to watch out for
    • @joachim.zell: it should be intuitive, easy to understand, pave our own path so to speak. Should find a guinea pig not familiar to read through the docs.
    • @sdyer : quick 1 min videos would be really useful. But for now, focus on design decisions and outcomes.
  • How do we “archive” the work of the group - github repo, working docs, research, etc
  • It was generally agreed that wider “open” testing would not give useful feedback
  • Implementation group: looking for participants from software vendors, etc, as well as soliciting volunteers for leaders :wink:

Recording and Transcript

1 Like

Sorry I could not attend the last meetings.

Just wanted to throw two things:

You do a very great job on this, I can only applaud to all of you.

  1. Regarding Despill:

A tri-component camera follows the same physical rules in terms of colour mixing as the human observer, this means all Grassman’s laws are true for a camera as well, as long as we only use 3x3 matrices in the camera processing.

For our case here it means a mixture of two colours will always be on a straight line between the two colours (on a chromaticity plane). It cannot be somewhere else. So if we have a green background and brown (yellow) hair, all motion-blurred pixels lie exactly on a line (in chromaticity plane) connecting the hair and the green background.
If we apply a non-linear transformation to the image (like the compress Gamut) we destroy this behaviour. Therefore it is expected that things which rely on linearity will not work so great with gamut compressed images, and hence it is a good choice to have gamut compression as an optional component.

This is one of the major reasons I also strongly dislike the idea of more complex IDTs backed into the footage, it would produce unideal images for VFX and other processes which rely on Grassman’s laws.


Said it already but repeating again: Good job team! :slight_smile:

1 Like