Linux & HDR | KDE settings & Gaming experience

Seimus · 1 April 2025 23:51

Hey all,

After getting myself an AMD GPU, I felt more confident to try out HDR. And I was positively surprised, how good HDR is actually working on its current state on Linux. Saying that HDR on Linux has still a long way to go. BUT! Is totally usable and specifically on Desktop usage better than the Windows implementation from my view point.

The point of this Topic is to discuss HDR experience and provide if so possible best settings for non-HDR + HDR settings in KDE. Keep in mind with bellow settings you still have to tune the HDR per the game itself in the game HDR settings.

Most people using HDR in KDE most likely will ask themself 3 questions

1. What the hell are those extra slide option for?

“SDR Brightness” is, as the name suggests, the brightness KWin renders non-HDR stuff at, and effectively replaces the brightness setting that most displays disable when they’re in HDR mode
“SDR Color Intensity” is inspired by the color slider on the Steam Deck. For sRGB applications it scales the color gamut up to (at 100%) rec.2020, or more simply put, it makes the colors of non-HDR apps more intense, to counteract the bad gamut mapping many HDR displays do and make colors of SDR apps look more like when HDR is disabled

2. Why are the colors so flat, ugly, washed out and dimm when I enabled HDR??
The answer is rec.2020.

When you enable HDR it doesn’t use sRGB, P3 nor other monitor preconfigured color spaces. It uses the proper HDR rec.2020 color space. In HDR content this color space will make life shine bright and colorful. However, the problem is the DE and the non-HDR content will have “washed out colors” and your screen may look “dimm”.

In order to combat that we can use the “SDR Color Intensity” & “SDR Brightness” sliders.

3. How the hell should I use them?
Even this second question is bit more subjective, cause it depends on personal preferences I think I found the sweet spot for HDR Enabled + HDR content + SDR content.

What I basically tried is to tune the visual to same level as is my SteamDeck OLED. This is because, Steam deck OLED has out of the BOX very vivid yet not so much over-saturated colors.

My Monitor is AW3423DWF
My GPU is 9070XT

How to enable HDR in games

You need a HDR capable monitor
You need to enable HDR in KDE using Wayland
You need to install gamescope
You need to run following steam launch command
Change your -w -h resolution per your monitor and set proper refreshrate -r

gamescope -w 3440 -h 1440 -f -r 165 --adaptive-sync --hdr-enabled --  %command%

The Settings

Monitor

For when HDR is disabled there are 2 profiles to consider.

The first one will cap the color space to sRGB, but it will be the most accurate representation of white balance, colors, and color temperature.

Color accuracy - Pure sRGB - Creator > sRGB + Gamma 2.2
You can as well set P3 but actually doesn’t matter cause we will keep HDR in KDE always ON. If you will disable HDR and want more colors P3 in pure SDR is good. Also is very important to point out my monitor is factory calibrated for sRGB and P3 out of the box. This may not be the fact for every monitor

The second one will be less accurate in regards of colors and white balance but will give you more vivid colors. Yet still will keep more true to real colors than the Standard preset.

Vivid colors - Less accurate - Custom > Gain > 97-98-100
The gain is per each monitor different, it really depends on the monitors panel

Rest of the settings:

Everything else is off/default
Brightness/Contrast both at 75%
HDR modes:
- Peak 1000 - HDR1000
- True Black - HDR400

KDE Plasma 6.3 - Display configuration

Peak 1000 - HDR1000

This HDR mode and settings should you give the best experience for peak highlight brightness. It really makes the details !POP! like; fire, explosions etc.

The downside to this is something called ABL. Some people do not see it some do, and it mainly depends on the content you are using it on. When for example you have a darker scene ABL will not kick in. But if you have a brighter scene ABL will kick in and the overall picture may look a bit dimmed compared when HDR is turned off this will be more visible in SDR.

If that’s the case and you want to still use HDR you can use the True Black - HDR400 mode.

HDR enabled
Color accuracy - Prefer efficiency
The other mode has performance impact
sRGB Color Intensity ~50%
My is set to 50% exactly currently
Maximum SDR Brightness 240-300
My is set to 300 exactly currently. This setting is very subjective
Brightness 75%
This setting should be same as brightness in the Monitor settings

True Black - HDR400

This HDR mode caps the MAX brightness at 400nits. Meaning highlights will not !POP! so much as in the first mode, but its not prompt to ABL.

HDR enabled
Color accuracy - Prefer efficiency
The other mode has performance impact
sRGB Color Intensity ~50%
My is set to 50% exactly currently
Maximum SDR Brightness 200-250
My is set to ~250. This setting is very subjective
Brightness 75%
This setting should be same as brightness in the Monitor settings

With that I believe is achieved a very good balance between color accuracy and color vividness.

Yet keep in mind its all subjective.

Seimus · 20 June 2025 08:16

Update Jun 20th 2025

Today new Plasma version 6.4 came out, which brought few new settings to HDR, mainly the calibration mode and changed few settings with it.

I will have a look and play with it a bit and provide as well some settings reflecting the changes on Plasma 6.4 for HDR.

Seimus · 21 June 2025 18:00

KDE Plasma 6.4 - Display configuration

With 6.4 update KDE devs implemented an embed HDR calibration tool, that should help end users to properly yet easy to calibrate their HDR experience.

With this update the Maximum SDR Brightness is gone and is now part of the new Calibrate HDR Brightness option.

Calibrate HDR Brightness has two parts:

Peak HDR luminescence, (which displays often report wrong)

This shows a white square covering 10% of the display area at 10000 cd/m² (which the monitor limits to the maximum it can actually show), and the Plasma logo at a luminescence level configured by the user. When the brightness level is configured so that you just barely see the Plasma logo, then we’ve roughly reached the maximum brightness level.

Max SDR luminescence (previously knows as Maximum SDR Brightness)

This one changes what “100%” of the normal brightness slider means, and needs to be configured

low enough so that the monitor’s tone mapping doesn’t interfere with image quality
low or high enough to match user preference