Re: [csswg-drafts] Define rec2020 color space to use 2.4 gamma (#12574)

The CSS Working Group just [discussed](https://www.w3.org/2025/08/19-css-color-minutes.html#e11d) `Define rec2020 color space to use 2.4 gamma` and agreed to the following:

 * `RESOLUTION: make the change to 2.4 gamma for rec2020 unless it's not web compat`

<details><summary>The full IRC log of that discussion</summary>
ccameron: historically lot of confusion of rec709 and 2020 should use as gamma<br>
ccameron: lot more effort in the video world to say rec709 and 2020 when they are displayed referred use display gamma<br>
ccameron: display referred tell you how you go from pixel value to output light<br>
<TabAtkins> ccameron: in contrast with scene referred<br>
ccameron: proposal is to get 2020 definition to 2.4 gamma<br>
ccameron: apple has changed already to use 2.4 gamma AFAIK<br>
ccameron: we could solve this long historic confusion by switching to 2.4<br>
ccameron: we could also do it for 709<br>
ChrisL: yes should be a separate discussion<br>
ChrisL: BBC agrees its the right thing<br>
ChrisL: concern is that it was added in 2016 and its very visible change<br>
ChrisL: it changes color<br>
ChrisL: trying to look on WebArchive for data about compat but we dont have this data<br>
ChrisL: so people will need to update if there is any usage and also for WPT<br>
florian: can we resolve in a way that its only if web compatible<br>
lea: i would be surprised if its not web compat<br>
lea: new color formats takes a very long time to be adopted by authors, e.g. even HSL which has existed for decades has surprisingly low numbers<br>
ChrisL: lets do this<br>
proposal: make the change to 2.4 gamma for rec2020 unless it's not web compat<br>
ChrisL: it doesnt change rec 2100<br>
`RESOLUTION: make the change to 2.4 gamma for rec2020 unless it's not web compat`<br>
</details>

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Received on Tuesday, 19 August 2025 13:34:05 UTC