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So, I searched, and I find a few older reports on a similar issue (dating from 2020ish) but when I enable HDR in the Vulkan settings, Doom just ends up looking extremely washed out. I'm playing on an HDR-capable display, and don't have that issue with other games (with the exception of one, Ghost Recon: Breakpoint, which acts extremely similarly, washing everything out when HDR is enabled). I'm on Windows 11.

I took screenshots, and the screenshots preserve accurately what it looks like.
Without HDR:


With HDR:

Yep, the HDR setting is broken at the moment.

I'll probably fix it once I have a HDR monitor again to test with. Unfortunately Dell wouldn't ship me their QD-OLED monitor until August I believe it was, so until then I can't fix it.

Gotcha. I take it it wasn't the srgb to linear fix mentioned in the older thread?

Honestly I'm not sure exactly what is wrong. It could be the tonemap/transfer function. Or it could be missing HDR metadata. Or both. Or something entirely different. The thing is that when I don't have the hardware and when the online documentation on the subject is hearsay at best there's no chance I can fix it.

The good news is that the Dell AW3423DW at least should have sufficiently good enough HDR capabilities that I can do actual tests. The Samsung Odyssey G9 I had at one point had so sad support I couldn't tell if the behavior at that time was the monitor or the engine. Only so much you can do when the "HDR" is backed by 3 zones.