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HDR Confusion (lemy.lol)

submitted 4 months ago* (last edited 4 months ago) by [email protected] to c/[email protected]

12 comments fedilink hide all child comments

Hey fellas, could you help me understand a bit more about HDR?

I understand that it's an absolute brightness standard, not like the relative levels in SDR
But why does it end up washing out colors unless I amplify them in kwin? Is just the brightness absolute in nits, but not the color?
Why does my screen block the brightness control in HDR mode but not contrast? And why does the contrast increase the brightness of highlights, instead of just split midtones towards brighter and darker shades?
Why is truehdr400 supposed to be better in dark rooms than peak1000 mode?
Why is my average emission capped at 270nits, that seems ridiculously low even for normal SDR screens as comparison.

Cheers 😊

Edit: It's a QD OLED

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[–] [email protected] 7 points 4 months ago (2 children)

I understand that it's an absolute brightness standard, not like the relative levels in SDR

The standard is also relative brightness actually, though displays (luckily) don't implement it that way.

why does it end up washing out colors unless I amplify them in kwin? Is just the brightness absolute in nits, but not the color?

It depends. You might

have a driver bug. Right now only AMD has correct color space communication with the display, that doesn't work correctly on Intel and NVidia yet
have a display that does a terrible job at mapping the rec.2020 color space to the display
be just used to the oversaturated colors you get with the display in SDR mode

Why does my screen block the brightness control in HDR mode but not contrast?

Because displays are stupid, don't assume there's always a logical reason behind what display manufacturers do. Mine only blocks the brightness setting through DDC/CI, but not through the monitor OSD...

Why is my average emission capped at 270nits, that seems ridiculously low even for normal SDR screens as comparison

OLED simply gets very hot when you make it bright over the whole area, the display technology is inherently limited when it comes to high brightness on big displays

[–] [email protected] 1 points 4 months ago (1 children)

Hey there, thanks for the comprehensive reply, I learned a lot. Also, your blog is fantastic, I'm always happy when there's a new post =)

Question about the last point: I feel like in SDR mode, the OLED is pushing brighter images. I almost feel like it's underselling the capabilities at 270, but does so to give pixels a rest every now and then, in the hope that the bright spots don't stay stationary on the screen. It's a wild guess, I have no idea.

[–] [email protected] 3 points 4 months ago

Also, your blog is fantastic, I'm always happy when there's a new post =)

Thank you, I'm glad you like it!

I feel like in SDR mode, the OLED is pushing brighter images. I almost feel like it's underselling the capabilities at 270, but does so to give pixels a rest every now and then, in the hope that the bright spots don't stay stationary on the screen. It's a wild guess, I have no idea.

It's certainly possible, displays do whacky stuff sometimes. For example, if the maximum brightness in the HDR metadata matches exactly what the display says would be ideal to use, my (LCD!) HDR monitor dims down a lot, making everything far, far less bright than it actually should be.

KWin has a workaround for that, but it might be that your display does the same thing with the reported average brightness.