After reboot my Steam Deck yesterday evening, the external display to which it is connected showed an “HDR mode” notification in the middle of the screen for a moment. From that point on, SteamOS rendered way too bright, especially for an evening setting. We wanted to turn down the brightness. The display doesn’t allow reducing brightness when in HDR mode; brightness is defined by the device sending the video stream. I tried to use the brightness slider on the Steam Deck’s settings menu. It was disabled.
If adjusting brightness is not possible, then the next obvious thing to do was to turn off HDR mode1. I set out to find the toggle for this in settings, and right above it was what I really needed: an “SDR content in HDR mode” slider.
The slider worked exactly as expected. Great, no need to disable HDR.
But the experience hadn’t been great. This slider probably shouldn’t be hidden down at the end of the Display settings. In fact, the typical “brightness” slider should be repurposed to perform exactly this function. This slider won’t control brightness for game which support HDR; those games have an in-game slider. So the OS’s brightness slider, once adapted to control “SDR brightness in HDR mode” would need a little clarification underneath: “Does not apply to HDR games; see in-game menu”.
The first game we played did support HDR, and the first screen which is showed was one to properly adjust brightness for it. HDR is a really cool feature, but if brightness control is not a first-class feature, then the value of HDR quickly drops to a negative one.
Addendum
Huge thanks for everyone involved in getting HDR working on this software stack; I’m really pleased to see the improvements to the graphics stack that have been happening on Linux in recent times.
At this point, my eyes were already starting to hurt from starting at excessive brightness, so leaving HDR mode on was not an option. ↩︎