- From: simontWork via GitHub <noreply@w3.org>
- Date: Thu, 07 Aug 2025 16:02:10 +0000
- To: public-css-archive@w3.org
> > When [§ 9 Compositing SDR and HDR content](https://drafts.csswg.org/css-color-hdr/#Compositing-SDR-HDR), and for color space conversion, the HDR reference white for SDR content should be anchored at 203 cd/m² [[Rpt_BT.2408]](https://drafts.csswg.org/css-color-hdr/#biblio-rpt_bt2408) so that that the HDR reference white level of the inputs to compositing will end up at the HDR reference white level of the combined signal. I would argue that, as HLG is relative, you can choose a value of Lw and System Gamma such that diffuse white in HDR matches the SDR format. The HLG can then be displayed at any other level (with the correct system gamma) and the shadows and midtones will match between the HDR and SDR composites. This is what we did for the Color on the Web demos (with the bonus that if you match to sRGB, the system gamma is unity and can be ignored). -- GitHub Notification of comment by simontWork Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/12574#issuecomment-3164836222 using your GitHub account -- Sent via github-notify-ml as configured in https://github.com/w3c/github-notify-ml-config
Received on Thursday, 7 August 2025 16:02:10 UTC