Paalanen: Developing Wayland Color Management and High Dynamic Range

Posted Nov 20, 2020 3:10 UTC (Fri) by flussence (guest, #85566)
Parent article: Paalanen: Developing Wayland Color Management and High Dynamic Range

Wayland might be a chance to finally sort out this mess. I've got two monitors that support basic 30bpp input, one a decade old now, and it's never been safe to use on X because so many things make the assumption that every drawable is 24bit (some may even be assuming it can't be *lower*, but I don't want to check).

Of course, graphics drivers missing 30bpp support for years didn't help…

Paalanen: Developing Wayland Color Management and High Dynamic Range

Posted Nov 20, 2020 5:18 UTC (Fri) by epa (subscriber, #39769) [Link] (1 responses)

I think that’s a third issue. You can have 10 bits per channel (R,G,B) but still not accurately model the colour gamut provided by the monitor. If the computer produces a signal which is 100% red, 40% green and 20% blue, what exactly is that in terms of frequencies of light coming from the screen? Is there an exponential relation between the size of these numbers and the amount of light, and if so what is the gamma? And how are those perceived as colours by a human? All these questions apply equally whether you have 30 bit, 24 bit or even 6 bit output.

Paalanen: Developing Wayland Color Management and High Dynamic Range

Posted Nov 23, 2020 15:07 UTC (Mon) by imMute (guest, #96323) [Link]

>If the computer produces a signal which is 100% red, 40% green and 20% blue, what exactly is that in terms of frequencies of light coming from the screen? Is there an exponential relation between the size of these numbers and the amount of light, and if so what is the gamma? And how are those perceived as colours by a human?

All of this is defined in the EOTF of the color standard the computer and display are using. In SDR days, that was universally assumed to be sRGB (for color primaries) and gamma (transfer function). For HDR, it's some other set of primaries (maybe Rec. 2020) and either PQ or HLG (for the transfer function).

And yes, all of that is orthogonal to the bit depth of the data (other than PQ and HLG really needing at least 10 bits to be of sufficient quality).