Many people are, understandably, confused about brightness levels in content creation and consumption - both for SDR and for HDR content. Even people that do content creation as their job sometimes get it really wrong.
I should elaborate on why the “Peak white” stuff is wrong, they give this math here for mapping linear luminance. This can be really confusing, “what do we map the references to” well if PQ “graphics white” is 203, should we map sRGB to 203? clearly not, at least not always as implied by BT.2408.
the question as to what we map SDR content to in an HDR space is complex, and in many cases almost certainly not some number that we can do 1:1 mapping with, which is why specifications for inverse tonemapping exist. for instance BT.2446 defines multiple tone mapping algorithms to go from SDR->HDR->SDR or HDR->SDR->HDR or any step inbetween with minimal content loss and fidelity loss.
we cannot do a simple one size fits all function and expect everything to be hunky dory
I should elaborate on why the “Peak white” stuff is wrong, they give this math here for mapping linear luminance. This can be really confusing, “what do we map the references to” well if PQ “graphics white” is 203, should we map sRGB to 203? clearly not, at least not always as implied by BT.2408.
the question as to what we map SDR content to in an HDR space is complex, and in many cases almost certainly not some number that we can do 1:1 mapping with, which is why specifications for inverse tonemapping exist. for instance BT.2446 defines multiple tone mapping algorithms to go from SDR->HDR->SDR or HDR->SDR->HDR or any step inbetween with minimal content loss and fidelity loss.
we cannot do a simple one size fits all function and expect everything to be hunky dory