Notice of Meeting - ACES Gamut Mapping VWG - Meeting #13 - 5/21/2020

ACES Gamut Mapping VWG Meeting #13

Thursday, May 21, 2020
5:00pm - 6:0pm PT (Los Angeles time / UTC-12:00am)

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

  • 5/28/20 9:30am

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


  • The majority of the meeting was @jedsmith giving a nicely broken down demo of the components of his algorithm - he will be posting the script for reference, but please see the recording for full details

  • There was a lot of talk around what ‘success’ looks like: hue shifts? Fidelity of texture (grain)? Slope of compression curve for a given bit depth?

    • On hue shift:
      • @LarsB voiced concerns about the hue shifts caused by the non-uniform compression between the RGB channels
      • An argument against that was that within the “zone of trust” hue would be preserved.
      • Lars presented Munsell hue line plots in various color spaces to demonstrate the lack of hue linearity in all of them
    • On bit depth:
      • We did not really discuss it on the call, but we are in floating point scene linear in ACES. This might come into play in the output transform group. Open to opinions on this in the next meeting.
    • On texture/grain:
      • We did not really get to this, looking for tests to demonstrate the workability of the current algorithm as it pertains to grain
  • Should we be limiting to a gamut for reasonable values? (i.e. e-gamut) how much does it really help?

  • @Thomas_Mansencal brought up again the question of whether we should be compressing to a gamut of physically realisable colors. BT.2020 vs AP1?

  • When iterating on a particular algorithm we should start using version numbers to more easily identify which iteration is being discussed in forum posts

1 Like

I’ve uploaded the Nuke script used in the presentation to the gamut-compress git repository, if anyone wants to play around with it.


And @matthias.scharfenber was on the agreeing slope :wink:


@jedsmith and I have tagged our respective repositories with a v0.1 stamp. I took that opportunity to create a super-repo which pulls those versions and tag the whole thing:

@Alexander_Forsythe, @sdyer: I would be more than happy to transfer that over to the Academy, provided everybody is happy with that!