[Cin] Even more on HDR in video

[Andrew Randrianasulu]

https://lightillusion.com/what_is_hdr.html

This page points out something interesting:

you can have only *some* components of "HDR" in any particular display, so
for example display can be Wide Gamut bt2020 BUT SDR! And/or smaller than
4k ;)

===
Additionally, the individual aspects of the HDR specifications can, and
often are, used in isolation. For example, there is nothing to stop a
standard gamut display (Rec709), with standard HD or even SD resolution,
working with an HDR EOTF with high contrast range.
======

It also points out that viewing environment even more important for both
HDR schemas - PQ and HLG.

Interestingly it includes table where specific (integer!) signal levels
correspond to specific luminance in nits.

I still can't fully wrap my mind around what exactly "nit" represent, but
apparently in HDR you really grade relative to specific max/min luminance
of your mastering display AND suitable HDR display/TV must do some tone
mapping magic if your defined luminance (?) goes above level that
monitor/tv can show.

There was equation on page about tonemapping
https://64.github.io/tonemapping/

===

Converting a linear RGB triple to a luminance value is easy:
L=0.2126R+0.7152G+0.0722B

====

but I am not sure if it works for *any* useful RGB values?


Also, issue with viewing distance wil play differently for those VR setups?
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