Colorimetry is standardized. The W3C has been asking the same questions about mixing HDR and SDR, as have various other standards orgs like SMPTE: https://draf

Colorimetry is standardized. The W3C has been asking the same questions about mixing HDR and SDR, as have various other standards orgs like SMPTE: https://drafts.csswg.org/css-color-hdr/#Compositing-SDR-HDR https://drafts.csswg.org/css-color-hdr/#Compositing-SDR-HDR