(I wish I could link the study, but I found it during the peak of my 2012-era graphics career. Suffice to say, more devs should study the science of perceptual testing.)
Coincidentally in a YUV encoding I'd only push the V axis to 10 bit - maybe even 12 to cover extra HDR range, i.e. higher absolute brightness when the display supports it. (Or go with a logarithmic encoding, in which case even 8 bit might be enough...)
There must also be limits to perception or resolution. Are our eyes even able to tell the difference between FHD, 2K and 4K on a 15" screen?
I tested FHD vs 4K on a 31" screen and could not are a difference when watching a 10 minute video (I had 2 screens side by side for reference).
On a semi related note. I also tried watching 60fps videos at 60Hz vs 144Hz (again side by side) to test out my new screen. No difference. Even fast moving things.
I really feel like either I just don't perceive these things and it'll keep more money in my wallet, or that I'm not alone and everybody can save money. A chart of when differences actually become perceptible would be great. It wouldn't surprise me I'd the threshold for 4K were 42", 10bit only in grays and fps at a certain pixel per second movement speed.
The reasons why are interesting, but it has to do with how the eye processes images and color.
Remember, you can turn your screen as bright as you want. But it doesn't help the content appear more "real" or "better" or "HDR-like". Therefore, HDR is simply "the ability to discern between different levels of color." And if you try to measure exactly how many levels of color a human can discern, the answer is no more than the 256^3 available via 8-bit RGB.
The precise claim: if you have two screens next to each other, one 8-bit RGB and one 10-bit RGB, and both screens are color calibrated / brightness calibrated identically, and the viewing conditions are identical for both screens, then if you blindfold someone and put them in front of a random screen, they will be unable to say "Ah, this is the 10-bit RGB screen!" more than random chance.
10-bit also comes with much better calibration precision where the translation isn't done in the display itself.
I didn't say to turn down the brightness of the HDR screen. I said the brightness per area must match.
Using maximum brightness often harms color reproducibility too, by the way. So if you believe brighter = better, don't.
But that’s not what HDR is. 8bpc is definitely not enough to represent HDR Rec.2020 or DCI-P3 without significant banding.
Because 8 vs 10 bit colour in sky photography is quite obvious