Request for review and comments on v0.1 Draft of "ACES Output Transform Details"

technical-documents
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(Scott Dyer) #1

This is an open call to the community for review and comment on a document entitled “ACES Output Transform Details”. This document is essentially a catalog of the header information from the CTL files (plus a bit more).

Comments or suggestions on anything in the document are welcomed. I am aware that the “definitions” sections still need refinement - but suggestions for those are certainly welcome.

You can submit feedback in a reply here, mark-up the PDF with comments and send back, or, for those who are LaTeX savvy and want access to the source to make significant edits, I can provide a link where you can edit the document source.

There will be other documentation posted here to ACESCentral for review soon.

TB_2018_002_v0.2.pdf (256.7 KB) (file last updated 08/06/2018)

Summary:
This document summarizes each of the twenty-one Output Transforms available as presets to the user in ACES v1.1. The document provides the design characteristics for each transform, the intended display type and setup on which the output of each transform is intended to be viewed, and test values to confirm the proper pairing of transform and display configuration. Where necessary, notes specific to each Output Transform are provided to explain specific design decisions, caution against common misuse, and to obviate other common misunderstandings.

Thanks!


(Kevin Wheatley) #2

Section 9.1.3, 9.2.3, 9.3.3 and 9.4.3 Display Type of Dolby Cinema projector - at 1000/2000/4000 nits, I guess that is an error :slight_smile:

Looks like an error carried forward into a lot of the HDR tables.

If they really are for a dark environment I’d make a note that this is not the same as the ITU recommendations for viewing, ITU is not a dark environment - this applies especially to the HLG curve.

Kevin


(Scott Dyer) #4

@KevinJW, thanks for taking a close look and catching those copy/paste errors.

I’ve fixed the tables for the HDR and added some notes regarding both the surround and targeted mid-gray luminance for the HDR transforms, since our “preset” values in 1.1 do not match those recommended in BT.2100 or BT.2408-0.

I’ve updated the original post with the updated version.


(Jim Houston) #5

Hi Scott,

While looking through this, I noticed that the DCDM versions have the primaries for XYZ but a device white of DCI white. Since we are using the XYZ as a virtual device, the white point in use for the virtual encoding ‘device’ is illumE (0.33 0.33 0.33) since this is what is used for encoding in that color space. The limiting ACES values are still OK. In 5.7, the limiting primaries are OK with a limiting white of DCI because that is not the encoding but just a description of the gamut being used. The distinction about the 48/52.37 encoding of luminance is not noted in this section, though it is part of the referenced standard. (i.e. the values of full white is going to be different in each case and will never be 4096,4096,4096)