Notice of Meeting - ACES Gamut Mapping VWG - Meeting #29 - 9/17/2020

ACES Gamut Mapping VWG Meeting #29

Thursday, September 17, 2020
5:00pm - 6:00pm Pacific Time (UTC-12:00 Friday)

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

  • 9/24/20, 9:30am

Dropbox Paper link for this group:

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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.

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It’s rare that a production is willing to share content, especially content that was ‘difficult’, so I want to publicly thank Andrew Savinsky, a compositor on the Ukranian TV series ‘Sniffer’ who contacted me about the sequence below several years ago, for getting permission from Pronto Films, the content owner, to share this content for “demonstration purposes”.

The image below is threefold:

  • on the top, I’ve grabbed the ALEXA K1S1 rendering;
  • in the middle (grabbed from Nuke) the ACES P3D65 rendering without gamut mapping, and
  • on the bottom, the group’s gamut mapping algorithm with the default parameters.

I’m not sure images here appear at full resolution, but three full-resolution plates from this sequence have been uploaded to the group’s dropbox.


Thanks Joseph and thanks Andrew!!


  • @LarsB notes he’s already had to push the power coefficient below 1 - down to 0.5
  • @LarsB also notes that the algorithm causes noise crosstalk between channels, and can increase appearance (typically from blue to green). Suggested synthetic image to test.
  • @joseph recommends shooting an over/under for a test, also deliberately mess up the color balance in raw
  • @sdyer is uploading the Garlic film scan for us to take a look at to double check efficacy with film applications
  • @carolalynn stated a proposal for how we might run user testing, will surface this to the other time zone and add things to the dropbox paper with more info.
  • @carolalynn will also be sending a general “update” mail/post to ACES central and the original group list to elicit more feedback and source candidates for testing
  • @matthias.scharfenber showed his Nuke script with a modified shaper space to accommodate large negative values to then encapsulate the algorithm into a 3D LUT. We are not sure of the benefits of putting this out there, as it’s not the ideal implementation. But could be useful for OCIO 1.0 applications possibly, with many cautions and red flags and warning signs.

Recording and Transcript