Re: [EXTERNAL] Re: Proposal for HTMLCanvasElement HDR compositing modes

On Tue, 16 Mar 2021 at 15:44, Todd, Craig <> wrote:

> BT.2100 is a more complete specificaton as it includes specs on the
> reference display and reference environment.
> BT.709 display was de-facto CRT. When new display technologies became
> available it was necessary to explicitly define the HDTV display. This was
> done in two separate Recs, BT.1886 spec'd gamma=2.4 and BT.2035 specs white
> at 100 nits and a viewing environment with a 10-nit background. I consider
> HDTV a display referred system, i.e. you create a pixel to produce known
> color/luminance on the reference display in the reference environment.

yes, I'd actually consider 709/1886 display referenced too because  the
effective rendering transform from scene to display is defined in terms of
the viewing conditions, most edits made to the signal are made on a monitor
without transforming back to scene linear, and most outputs from cameras
today do not encode using the Rec 709 OETF in the first place, at least not
for any of the content we see.

Certainly when it comes to mapping content mastered in one set of reference
condition to the specific use cases we always map to reference display
colourimetry and then back through the new display/conditions on the
assumption that the mastering environment needs to be preserved and is
often unknown what the actual scene colorimetry might have been and what
transformations have been applied as a rendering.

I'd do pretty much the same approach for HLG, even though it is possible to
obtain HLG unedited from a camera and thus get some focal plane referred
relative scene linear, people want images to "look the same" as they saw on
some monitor, rather than some vague recollection of the scene. This
basically makes images practically display referenced the moment you edit
them whilst viewing on a monitor.


Kevin Wheatley · Head of Imaging

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Received on Tuesday, 16 March 2021 17:45:33 UTC