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

+Progress Report, ACES Gamut Mapping Virtual Working Group

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.

Upload link: Gamut Mapping Image Submission

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:

colour-science/gamut-mapping-ramblings

Gamut Mapping Ramblings. Contribute to colour-science/gamut-mapping-ramblings development by creating an account on GitHub.

github.com

colour-science/gamut-mapping-ramblings • github.com

Jed Smith Work:

Gamut Compression Git Repository

Release v0.1

Simple, fast, functional, invertible. Contains only “simple” Reinhard distance compression method

Release v0.2

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.

Release v0.3

Add Fuse version of GamutCompress tool. Works in Blackmagic Fusion Studio, DaVinci Resolve Studio, and DaVinci Resolve Lite.

Add Shadow Rolloff parameter. This reduces the effect of the gamut compression below the specified achromatic value. The idea is to reduce gamut compression of shadow grain. Shadow grain can have very large distances from achromatic, which can result in differences when inverting the transform. Altering shadow grain may also not be desirable in vfx workflows, especially in the inverse direction.

Add helper function to the Nuke nodes which assists in calculating the maximum distance from achromatic.

Update default max distance values according to most common digital cinema source gamuts. See this post on acescentral for more information.

Release v0.4

Remove all compression methods except powerp

Add parameter for power

Release v0.5

Add ACEScc to the working space options in the DCTL and Matchbox versions.

Threshold adjustment per component for all versions of the tool.

Add hexagonal compression mode based on @nick-shaw's variation. Instead of only compressing primary colors (RGB), secondary colors (CMY) are compressed as well. This results in less hue skew near the primary color vector.

Release v0.35

"Everything but the kitchen sink" version.

Includes all compression functions including power(p).

Add ACEScc to the working space options in the DCTL and Matchbox versions.

Threshold adjustment per component for all versions of the tool.

Add @nick-shaw's variation of the algorithm that compresses primary and secondary colors. This is exposed as the "hexagonal" checkbox.

DCTL version (thank you @Nick S!) (now merged into @Jed S repo)

Matchbox Shader version (now merged into @Jed S repo)

@Matthias S Work:

Nuke Script & AP0 test exrs

Thomas’ work is encapsulated in the Jupyter notebook above.

@Thomas M has created a super-repository to host and track the other repositories, including snapshots of their status as of each VWG meeting.

Relevant ACESCentral Posts:

RGB Saturation Gamut Mapping Approach and a Comp/VFX Perspective

I have made a Resolve DCTL version of @jedsmith’s BlinkScript. This allows it to run in real-time on moving footage.

community.acescentral.com

RGB Saturation Gamut Mapping Approach and a Comp/VFX Perspective • community.acescentral.com

Gamut Mapping in Cylindrical and Conic Spaces

Some interesting figures to see how both models distort the space. RGB Saturation Based Model - Threshold 0.5 HSV Control Based Model - Threshold 0.5 Cheers, Thomas

community.acescentral.com

Gamut Mapping in Cylindrical and Conic Spaces • community.acescentral.com

Super-Repository for Virtual Working Group Development Effort

Hi, As discussed during Meeting #13, we have created a super-repository to host and track-down the development effort of the Virtual Working Group in a version-controlled way. At the moment the repository has sub-modules for Jed and colour-science repositories with their respective implementations of the RGB Saturation model (and the now background-research HSV Control one). I have pulled and checkout the versions produced for Meeting #13 and Meeting #14 and tagged/released the corresponding ...

community.acescentral.com

Super-Repository for Virtual Working Group Development Effort • community.acescentral.com

Display Transform BLGs for Nuke for Gamut Compressor assessment

I have just uploaded to the DropBox the set of BLG files that I demonstrated during the Gamut Mapping VWG #16 (at about 45 minutes). The idea is that these will allow people to view the output of the gamut mapper through a variety of display transforms, and therefore hopefully judge its affect on image appearance in a way which is not tied to the ACES Output Transform. We want to avoid making “corrections” to the behaviour of the gamut mapper to compensate for e.g. hue skewing which is in fact ...

community.acescentral.com

Display Transform BLGs for Nuke for Gamut Compressor assessment • community.acescentral.com

Gamut Mapping Implementation Details

As discussed in meetings #17 and #18, our group needs to be discussing implementation details of the algorithm to the point at which it might affect the algorithm itself. This section is a working space to discuss pros and cons of different implementations and what that means for the production workflow. Please add opinions, new ideas, and examples freely.

Example 1: Algorithm as an addition to any AP0 → AP1 colorspace transform

Pro	Con
Consistent - always applied, always inverted	Hard to maintain
Requires no extra work for the end user for the 80% of use cases	It’s a very big change to core ACES functionality
	Big changes can equal big problems
	Harder to change default parameters
	Inversion of material not previously gamut compressed (e.g. CGI rendered in AP1) may introduce undesirable values
	No image processing operation (VFX and grading) are aware of the gamut expansion back out.
	In-Gamut AP1 values close to the gamut surfaces become illegal values, which should be avoided. This further reduces the working space.
	There may be situations where AP0 to AP1 conversion is desired but without gamut mapping applied.
	Would operate differently than other ACES CSC transforms

Example 2: Algorithm as Separate Operator

Pro	Con
Gives control to end user & pipeline authors to choose whether or not to gamut map	Hard to track - does a DI apply it? VFX house? To all plates or only the ones that need it?
Easy to implement, basically replaces the Blue Light LMT	Increased likelihood of continued misuse (forgetting to invert, double application, using at end of stack instead of right after the IDT)
Easier to change and adapt default parameters
Applicable only to shots with visual issues
different tuning for different projects: Live Action vs CGI

Example 3: Algorithm as Separate Operator but with Enforced Dependency on AMF

Pro	Con
Trackable, creates a closed loop on an ACES pipeline	AMF is still in the beginning stages of implementation, and isn’t adopted into some of the main use cases we’re targeting for this VWG (i.e. Nuke)
Easier to change and adapt default parameters	Given the slow speed of adoption of CLF by software vendors (considering it has always notionally been a required component of ACES) AMF adoption may be equally slow.
Easier to implement, basically replaces the Blue Light LMT but sourced via AMF	Difficult to track multiple streams that have been composited together.

Gamut Mapping Testing Framework

Build to be tested, as of meeting #28 is the “bare bones” version. This has no shadow roll-off, uses only the power(p) curve, and has threshold and distance defaults from the calculations in this Colab by @Matthias S.

Proposal:

For our initial round of testing, the ACES Gamut Mapping Architecture VWG would like to propose “operation” based testing with controlled scenarios.

10 compositors, 10 colorists

Set footage (tables below)

Set operations: top 3 comp, top 3 grading (listed in tables below)

Locked “controls” (threshold, max distance, possibly compression too?)

Project setups in Nuke, Baselight, Resolve

Nuke: Matthias, Carol

Baselight: Nick, Daniele

Resolve: JZ, Pablo

Feedback via Google Form

Tell us your setup (Monitor, application & version, OS, etc)

Goals:

Get feedback from a smaller group to catch possible issues (both in the algorithm and in the test setups)

Limit customization to get feedback on default settings we’ve objectively chosen

Start to aggregate data for group report

Get initial feedback to seed implementation group

Non-goals:

“Visual” feedback:

We want to avoid how it “looks” by default, focus on how it helps work

Avoids complications in conjunction with the RRT/ODT

Compositing Tests:

Operation	Details	Test Image/Footage
Pull Matte - Bluescreen		motion blur hand, blurred lights
Degrain
Blurs, Glows & Defocus (bokeh)

Grading Tests:

Operation	Details	Test Image/Footage
Degrain
Alpha Blending
Blurs
HSL Qualifiers	e.g. aesthetic adjustments of corrected OOG colours	Fabian Matas nightclub
Hue curves	e.g. aesthetic adjustments of corrected OOG colours	Fabian Matas nightclub

Group Proposal

Failed to load Dropbox embed preview.

Working Group Proposal

Working Group Documents

Failed to load Dropbox embed preview.

02/02/20 - Some Initial thoughts from Daniele Siragusano

External Paper Resource Links

Color Space Conversion for the Laser Film Recorder Using 3-D LUT

Download Citation | Color Space Conversion for the Laser Film Recorder Using 3-D LUT | A new method of color space conversion for the laser film recorder is proposed. The input image file (10 bits or more, RGB) is converted by a... | Find, read and cite all the research you need on ResearchGate

www.researchgate.net

Color Space Conversion for the Laser Film Recorder Using 3-D LUT • www.researchgate.net

Papers describing gamut mapping algorithms using a core/confidence gamut:

Sara J. J. (1984) The Automated Reproduction of Pictures with Nonreproducible Colors, Ph.D. Thesis, Massachusetts Institute of Technology.

Katoh N. (1994) Practical method for appearance match between soft copy and hard copy, Proceedings of SPIE, vol. 2170, pp. 170–181.

Spaulding K. E., Ellson R. N., Sullivan J. R. (1995) UltraColor: A New Gamut Mapping Strategy, SPIE Proceedings, vol. 2414, pp. 61–68.

Katoh N., Ito M. (1999) Applying Non–Linear Compression to the Three–Dimensional Gamut Mapping, IS&T/SID 7th Color Imaging Conference, Scottsdale, AZ, pp. 155–159.

MacDonald L. W., Morovič J., Xiao K. (2001) A Topographic Gamut Compression Algorithm, Journal of Imaging Science and Technology, vol. 46, no. 3, pp. 228–236.

Lammens J., Morovič J., Nielsen M. and Zeng H. (2005) Adaptive re–rendering of CMYK separations for digital printing, AIC '05, Granada, Spain, 1211–1214.

Hersch R. D., Donzé P., Chosson S. (2007) Color images visible under UV light, Proc. Siggraph 2007, ACM Trans. Graph. vol. 26, No. 3, Article 75 (July 2007)

Casella S. E., Heckaman R. L., Fairchild M. D., Sakurai M. (2008) Mapping Standard Image Content to Wide-Gamut Displays, IS&T/SID 16th Color Imaging Conference, Scottsdale, AZ, pp. 106–111.

Proposed Test Shoot Scenarios

Example:

Additive mixing should work intuitively:

a reflective surface is lit by neutral ambient light

a narrow bandwidth light source (e.g. blue led) is shining on the reflective surface

part of the surface is shaded from the light source by an opaque object

the shadow of the object should appear “darker” than the area lit by the narrow band light source

Next Meeting

The next meeting of the Gamut Mapping VWG is scheduled for:

TBD

We use GoToMeeting for our conference calls and we record and then post each meeting so the community can review. Instructions for GoToMeeting are here:

​​Document Workspace

​​Problem

​​Scope

​​Anticipated Deliverable(s)

​​Documents

​​​+Progress Report, ACES Gamut Mapping Virtual Working Group​

​​Gamut Mapping Image Submissions

​​Gamut Mapping Algorithm WIPs

​​Gamut Mapping Implementation Details

​​Gamut Mapping Testing Framework

​​Proposal:

​​Group Proposal

​​Working Group Documents

​​External Paper Resource Links

​​Proposed Test Shoot Scenarios

​​Next Meeting

​​Past Meetings

​​Meeting #37 - December 10th, 2020

​​Meeting #36 - December 3rd, 2020

​​Meeting #35 - November 19th, 2020

​​Meeting #34 - November 12th, 2020

​​Meeting #33 - November 5th, 2020

​​Meeting #32 - October 8th, 2020

​​Meeting #31 - October 1st, 2020

​​Meeting #30 - September 24th, 2020

​​Meeting #29 - September 17th, 2020

​​Meeting #28 - September 10th, 2020

​​Meeting #27 - September 3rd, 2020

​​Meeting #26 - August 27th, 2020

​​Meeting #25 - August 20th, 2020

​​Meeting #24 - August 13th, 2020

​​Meeting #23 - August 6th, 2020

​​Meeting #22 - July 30th, 2020

​​Meeting #21 - July 23, 2020

​​Meeting #20 - July 16, 2020

​​Meeting #19 - July 9, 2020

​​Meeting #18 - June 25, 2020

​​Meeting #17 - June 18, 2020

​​Meeting #16 - June 11, 2020

​​Meeting #15 - June 4, 2020

​​Meeting #14 - May 28, 2020

​​Meeting #13 - May 21, 2020

​​Meeting #12 - May 14, 2020

​​Meeting #11 - May 7, 2020

​​Meeting #10 - April 16, 2020

​​Meeting #9 - April 9, 2020

​​Meeting #8 - April 2, 2020

​​Meeting #7 - March 26, 2020

​​Meeting #6 - March 19, 2020

​​Meeting #5 - March 12, 2020

​​Meeting #4 - March 5, 2020

​​Meeting #3 - Feb 27, 2020

​​Meeting #2 - Feb 20, 2020

​​Meeting #1 - Jan 30, 2020

​​Group Norms

​​How the ACES VWG Process Works

Document Workspace

Problem

Scope

Anticipated Deliverable(s)

Documents

+Progress Report, ACES Gamut Mapping Virtual Working Group

Gamut Mapping Image Submissions

Gamut Mapping Algorithm WIPs

Gamut Mapping Implementation Details

Gamut Mapping Testing Framework

Proposal:

Group Proposal

Working Group Documents

External Paper Resource Links

Proposed Test Shoot Scenarios

Next Meeting

Past Meetings

Meeting #37 - December 10th, 2020

Meeting #36 - December 3rd, 2020

Meeting #35 - November 19th, 2020

Meeting #34 - November 12th, 2020

Meeting #33 - November 5th, 2020

Meeting #32 - October 8th, 2020

Meeting #31 - October 1st, 2020

Meeting #30 - September 24th, 2020

Meeting #29 - September 17th, 2020

Meeting #28 - September 10th, 2020

Meeting #27 - September 3rd, 2020

Meeting #26 - August 27th, 2020

Meeting #25 - August 20th, 2020

Meeting #24 - August 13th, 2020

Meeting #23 - August 6th, 2020

Meeting #22 - July 30th, 2020

Meeting #21 - July 23, 2020

Meeting #20 - July 16, 2020

Meeting #19 - July 9, 2020

Meeting #18 - June 25, 2020

Meeting #17 - June 18, 2020

Meeting #16 - June 11, 2020

Meeting #15 - June 4, 2020

Meeting #14 - May 28, 2020

Meeting #13 - May 21, 2020

Meeting #12 - May 14, 2020

Meeting #11 - May 7, 2020

Meeting #10 - April 16, 2020

Meeting #9 - April 9, 2020

Meeting #8 - April 2, 2020

Meeting #7 - March 26, 2020

Meeting #6 - March 19, 2020

Meeting #5 - March 12, 2020

Meeting #4 - March 5, 2020

Meeting #3 - Feb 27, 2020

Meeting #2 - Feb 20, 2020

Meeting #1 - Jan 30, 2020

Group Norms

How the ACES VWG Process Works