[css-color-hdr] Where is the rec2100-pq/linear black luminance coming from?

[swick]

The title almost says it all. The spec defines the black level as 0.001 nit.

https://drafts.csswg.org/css-color-hdr/#valdef-color-rec2100-pq

White luminance 	203 cd/m²
Peak white luminance 	10,000 cd/m²
Black luminance 	0.001 cd/m² 

ST 2084 defines the black luminance at 0 nit, but it also is not defining a viewing environment so that isn't completely weird to me.

Wikipedia says black luminance is at 0.0001 nit for some reason.

Rec. 2100 says

Minimum luminance of display (black level) ≤ 0.005 cd/m2

[svgeesus]

I will need to look into this, thanks for raising the issue though.

[svgeesus]

So BT.2100 should be the defining reference, and it states ≤ 0.005 cd/m² but also requires a PLUGE to set the black level (presumably for narrow-range signalling). The actual measured black luminance will therefore depend onthe viewing flare, which is not directly stated.

[svgeesus]

I'm still not finding a source for the 0.001.

[svgeesus]

Changed to ≤ 0.005 cd/m²