- From: Sebastian Wick via GitHub <sysbot+gh@w3.org>
- Date: Mon, 24 Jun 2024 11:41:37 +0000
- To: public-css-archive@w3.org
> Which the viewing display is supposed to follow as closely as possible, right? No, this is probably the part that is so problematic. The reference display and viewing environment are in practice only followed when content is mastered but not when it is consumed. The solution has always been to "add a re-rendering step (OOTF) to account for non-reference viewing conditions" and is done by backlight/brightness/contrast control on displays most of the time. The quote is from css-color-hdr (https://drafts.csswg.org/css-color-hdr/#Compositing-SDR-HDR). This is also exactly how SDR content is handled. sRGB has a reference viewing environment and a reference display which means an sRGB signal is "absolute luminance", but people do constantly re-render sRGB because they view it in varying viewing conditions. My point here is that if you call PQ an absolute luminance signal, so is sRGB. It's not wrong to call them absolute luminance if you understand that this is only the case with a fixed display and viewing environment. If you have a variable viewing environment, neither sRGB nor PQ content should produce a constant luminance because the entire goal of the exercise here is to preserve the appearance. Even more concerning, if you have an HLG signal and a fixed viewing environment, isn't the HLG signal not also producing absolute luminance? The whole point I want to make here is that luminance is always absolute. If you have a fixed viewing environment and fixed display every signal produces absolute luminance. What differentiates PQ and HLG isn't "absolute luminance", it is that PQ is display-referred and HLG is scene-referred. > But that's irrelevant from the POV of the spec, which defines a 1:1 mapping of input signal to luminance. Don't you agree? No, see above. Even the spec currently allows for a color re-rendering step. -- GitHub Notification of comment by swick Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/10460#issuecomment-2186376578 using your GitHub account -- Sent via github-notify-ml as configured in https://github.com/w3c/github-notify-ml-config
Received on Monday, 24 June 2024 11:41:38 UTC