RE: Proposal for HTMLCanvasElement HDR compositing modes

Hi Chris,

If we look at Annex 1 of ITU-R BT.2100, then we can see that any form of Display Light needs to have had an OOTF applied (either in the camera/post-processing or display) and that applying the inverse OETF takes you from a non-linear signal to what is called in BT.2100 “Scene-light”.  This is similar to AMPAS ACES.

As the scene light may have artistic controls applied, perhaps “quasi-scene light”, “artistically adjusted scene-light” or “linear camera sensor-referred” may be a better choice?

Simon

Simon Thompson
Senior R&D Engineer

BBC Research & Development

From: Christopher Cameron <ccameron@google.com>
Sent: 16 March 2021 18:56
To: Simon Thompson-NM <Simon.Thompson2@bbc.co.uk>
Cc: Lars Borg <borg@adobe.com>; public-colorweb@w3.org; Pierre-Anthony Lemieux <pal@sandflow.com>
Subject: Re: Proposal for HTMLCanvasElement HDR compositing modes

On Tue, Mar 16, 2021 at 5:09 AM Simon Thompson-NM <Simon.Thompson2@bbc.co.uk<mailto:Simon.Thompson2@bbc.co.uk>> wrote:
Hi all,

If the definitions are changed from those published by the ITU, then there’s a great risk of confusion.  You would have a document referencing and defining how a video standard should be implemented using different terminology to the video standard itself.

The definitions are agreed at ITU and if a change is needed, then an ITU liaison to the relevant group should be made.

Please provide a link to where the ITU provides a succinct, universal, and precise definition of the terms used in the document so that we can ensure that the definitions are precisely the same.