Re: [EXTERNAL] Re: Specifying an API to query the display color volume

Most displays I've worked with are not adjustable. Desktop monitors are
notorious for this. The VESA HDR conformance actually tests that the
monitor in its default state behaves as specified by PQ where a certain
signal level must result in a specific amount of nits which makes very
little sense given that those monitors almost never are actually used in a
reference viewing environment. The engineers working on those displays and
on VESA also seem to be unaware that the viewing environment is still a
thing with a PQ system and simply do not even allow you to compensate for
it at all. Windows actually just invented its own "PQ" system and they
adjust the signal level based on user settings. This has some obvious
downsides as well that would go away if the displays were properly designed.

On Wed, Sep 13, 2023 at 1:17 PM Seeger, Chris (NBCUniversal) <
Chris.Seeger@nbcuni.com> wrote:

> This is merely a reference mode (for reference viewing conditions). HLG
> and SDR also have reference conditions even though they are scene referred.
>
> Most PQ displays I have worked with are adjustable.  Plus, Dolby Vision
> IQ, other picture modes alter luminance.
>
> I prefer this vs an HLG OOTF which is darker than a typical SDR consumer
> display if the HLG display is darker than 1Knit peak.
>
> Chris Seeger NBCUniversal, LLC
> Director, Advanced Content Production
>
> Get Outlook for iOS <https://aka.ms/o0ukef>
> ------------------------------
> *From:* Andrew Somers <andy@generaltitles.com>
> *Sent:* Wednesday, September 13, 2023 1:51:36 AM
> *To:* Pekka Paalanen <pekka.paalanen@collabora.com>
> *Cc:* Lars Borg <borg@adobe.com>; public-colorweb@w3.org <
> public-colorweb@w3.org>; Pierre-Anthony Lemieux <pal@sandflow.com>
> *Subject:* [EXTERNAL] Re: Specifying an API to query the display color
> volume
>
>
>
>
>
>
> *However, I'm confused by claims that PQ monitors would display the input
> signal nit-for-nit up to capability and lack end user adjustments. That
> would mean any adaptation to the actual viewing environment would need to
> happen at the video signal source. My monitor indeed disables brightness
> and contrast adjustments in PQ HDR mode.*
>
>
> Yea this. I have been confused by Dolby’s decision making here. It is as
> if to assume that there is a single environment that all PQ displays shall
> be in… Sure that works for commercial cinema—but only because of the
> evolution of *film* technology and the practical limits on film-projector
> brightness, which demanded a blackout viewing condition.
>
> Well… that ain’t today…
>
> 😳😎
>
>
>
> Andrew Somers
> Senior Color Science Researcher
> *Redacted for public list*
>
> On Sep 12, 2023, at 6:01 AM, Pekka Paalanen <pekka.paalanen@collabora.com>
> wrote:
>
> On Tue, 12 Sep 2023 03:21:36 +0000
> Lars Borg <borg@adobe.com> wrote:
>
> How about this:
> Start with standardized values, from maybe 40 to 10,000.
> (Such as 48, 80, 100, 160, 203, 235, 300, 500, 600, 720, 1000)
> If some standard values are close together, fake example 200 and 203, drop
> one.
> Fill in large gaps (> 40%? increment) with intermediate values
>
> These values would be max luminance for small patches.
> Some displays can return this value over HDMI, but the value must be
> mapped to the limited set to prevent fingerprinting.
>
>
> Hi,
>
> are you perhaps referring to EDID CTA-861-H: HDR Static Metadata Data
> Block?
>
> I'd just like to point out that this block in question defines
> "desired" luminance levels. I don't think it is any kind of promise of
> emitted luminance levels.
>
> My HP Pavilion 27" quantum dot monitor was advertised with 400 cd/m²
> luminance, but the EDID says desired max luminance is 600 cd/m², for
> example, and with desired max frame-average luminance of 350 cd/m².
>
> In other words, it does not look like these numbers would be usable to
> correlate with actual viewing environments, assuming you had
> information about the actual viewing environment.
>
> Then again, that's just one example that could as well be explained by
> EDID being incorrect, as EDID generally is notorious for.
>
>
> No ambient info, as:
>
>  *   this would require a measurement device.
>  *   Standardized mastering display color volume does not include it
>
>
> SMPTE ST 2086 mastering display information does not include it, but
> BT.2100 does give guidelines about it in "Reference viewing environment
> for critical viewing of HDR programme material". I guess assuming that
> is the best guess.
>
> The PQ system uses a display-referred signal, so one could say the
> signal needs to be displayed as encoded literally. But displays have
> different capabilities, not to mention different viewing environments.
> The PQ system can use ST 2086 metadata to describe the display it was
> mastered for, and BT.2100 recommends a viewing environment, so these
> should define the intended appearance which could be mapped to the
> display at hand in the actual viewing environment.
>
> However, I'm confused by claims that PQ monitors would display the
> input signal nit-for-nit up to capability and lack end user
> adjustments. That would mean any adaptation to the actual viewing
> environment would need to happen at the video signal source. My monitor
> indeed disables brightness and contrast adjustments in PQ HDR mode.
>
>
> Thanks,
> pq
>
>
>