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I'm not really convinced by this argument. Isn't the actual issue that SDR content tends to be mapped so that 0 is the darkest colour the TV can display and 1.

I'm not really convinced by this argument. Isn't the actual issue that SDR content tends to be mapped so that 0 is the darkest colour the TV can display and 1.0 is the brightest colour the TV can display? When an HDR signal comes along, then of course the brightest element it can display isn't any brighter than 1.0 was in the SDR image. This has the effect of the scene being overall darker in order to give more headroom for brighter elements to be brighter. But what is the other option? Have SDR content be dimmer than what the HDR monitor would otherwise be capable of displaying? I doubt you will get as many sales as your competition with that approach because the TV that renders SDR as bright as it can will always look better. (I do understand that there are some caveats relating to the fact that max brightness is different depending on the amount of the screen covered in brightness, but I don't think it's actually relevant to this argument overall)

jorvi 2y ago
The real problem is that 400-600 nits is allowed to be called a “HDR-certified” display. For “real” HDR you want at least 800 nits, ideally 1000. Otherwise you have to do what is stated upthread, latch max brightness to whatever your maximum nits is and make everything else very dark to keep the relative contrast intact.
blep-arsh 2y ago
I'm not an expert on the matter but Apple went with 1.0 for full SDR brightness, so you have to query for the maximum display brightness and explicitly use RGB values > 1.0 for HDR. This particular approach might not be a good idea for TVs but this kind of mapping seems easy to reason about and just makes a lot of sense to me. And since this does limit brightness for non-HDR-aware apps and content people figured out they can cover the screen with a multiplying overlay to boost the brightness up to the max.

jorvi 2y ago

The real problem is that 400-600 nits is allowed to be called a “HDR-certified” display. For “real” HDR you want at least 800 nits, ideally 1000. Otherwise you have to do what is stated upthread, latch max brightness to whatever your maximum nits is and make everything else very dark to keep the relative contrast intact.

blep-arsh 2y ago

I'm not an expert on the matter but Apple went with 1.0 for full SDR brightness, so you have to query for the maximum display brightness and explicitly use RGB values > 1.0 for HDR. This particular approach might not be a good idea for TVs but this kind of mapping seems easy to reason about and just makes a lot of sense to me. And since this does limit brightness for non-HDR-aware apps and content people figured out they can cover the screen with a multiplying overlay to boost the brightness up to the max.