Bug 507439

Summary:	HDR calibrator fails to detect peak brightness unless ICC profile set to built-in first
Product:	[Applications] systemsettings	Reporter:	Christopher Snowhill <kode54>
Component:	kcm_kscreen	Assignee:	kscreen-bugs-null <kscreen-bugs-null>
Status:	RESOLVED WORKSFORME
Severity:	normal	CC:	nate, plasma-bugs-null, xaver.hugl
Priority:	NOR
Version First Reported In:	6.4.3
Target Milestone:	---
Platform:	Arch Linux
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:

Description Christopher Snowhill 2025-07-24 12:10:38 UTC

SUMMARY
When configuring an HDR display for the first time, the settings applet does not have the correct peak brightness in the HDR calibrator, as detected from the display EDID, unless the display is left off HDR mode and the color profile is set to monitor built-in and applied first. Then it will have the HDR peak brightness correctly read from the monitor.

STEPS TO REPRODUCE
1. Attach an HDR monitor. (in this case, an Asus XG27UCS)
2. Configure the display to HDR mode.

OBSERVED RESULT
The display in HDR calibrator will not have a properly read peak brightness level from the EDID.

EXPECTED RESULT
The display should read the initial peak brightness level from the EDID.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Arch Linux
KDE Plasma Version: 6.4.3
KDE Frameworks Version: 6.16.0
Qt Version: 6.9.1

ADDITIONAL INFORMATION
I was able to somehow make the settings panel absorb my monitor's factory calibrated peak brightness level of 486 nits, by setting the monitor to SDR again, then setting the ICC profile to monitor built-in and applying. Then when I enabled HDR, the peak brightness was correctly set.

Comment 1 Zamundaaa 2025-09-26 16:01:41 UTC

I can't replicate that here, the default value matches the one from the EDID.

Please remove the peak brightness override from the calibration page (kscreen-doctor output.1.maxBrightnessOverride.disable) and then attach the output of kscreen-doctor -o here

Comment 2 Christopher Snowhill 2025-09-27 11:57:51 UTC

I can't reproduce it any longer, so I'm going to mark this as such.

```
Output: 1 DP-1 d0a9f63f-3e58-4dca-b04d-58294a36774e
	enabled
	connected
	priority 1
	DisplayPort
	replication source:0
	Modes:  1:3840x2160@60!  2:3840x2160@160*  3:3840x2160@144  4:3840x2160@120  5:3840x2160@120  6:3840x2160@120  7:3840x2160@100  8:3840x2160@60  9:3840x2160@60  10:3840x2160@50  11:3840x2160@30  12:3840x2160@30  13:3840x2160@25  14:3840x2160@24  15:3840x2160@24  16:2560x1440@160  17:2560x1440@120  18:2560x1440@60  19:1920x1200@60  20:1920x1080@120  21:1920x1080@120  22:1920x1080@100  23:1920x1080@60  24:1920x1080@60  25:1920x1080@60  26:1920x1080@50  27:1920x1080@30  28:1920x1080@30  29:1920x1080@25  30:1920x1080@24  31:1920x1080@24  32:1600x1200@60  33:1680x1050@60  34:1280x1024@60  35:1440x900@60  36:1280x960@60  37:1280x800@60  38:1280x720@60  39:1280x720@60  40:1280x720@60  41:1280x720@50  42:1024x768@75  43:1024x768@60  44:800x600@75  45:800x600@60  46:720x576@50  47:720x576@50  48:720x480@60  49:720x480@60  50:720x480@60  51:720x480@60  52:640x480@75  53:640x480@60  54:640x480@60  55:640x480@60  56:1600x1200@160  57:1280x1024@160  58:1024x768@160  59:2560x1600@60  60:2560x1600@160  61:1920x1200@160  62:1280x800@160  63:3200x1800@60  64:3200x1800@160  65:2880x1620@60  66:2880x1620@160  67:1920x1080@160  68:1600x900@60  69:1600x900@160  70:1368x768@60  71:1368x768@160  72:1280x720@160 
	Geometry: 0,0 1920x1080
	Scale: 2
	Rotation: 1
	Overscan: 0
	Vrr: Automatic
	RgbRange: Automatic
	HDR: enabled
		SDR brightness: 203 nits
		SDR gamut wideness: 0%
		Peak brightness: 486 nits
		Max average brightness: 486 nits
		Min brightness: 0.0969 nits
	Wide Color Gamut: enabled
	ICC profile: none
	Color profile source: EDID
	Color power preference: prefer efficiency and performance
	Brightness control: supported, set to 100% and dimming to 100%
	DDC/CI: allowed
	Color resolution: automatic (10), range: [8; 16] bits per color
	Allow EDR: unsupported
Output: 2 DP-2 edd03ce9-e04e-4b8a-b059-21bfc6db47aa
	enabled
	connected
	priority 2
	DisplayPort
	replication source:0
	Modes:  73:3840x2160@60*!  74:3840x2160@30  75:2560x1440@60  76:1920x1200@60  77:1920x1080@60  78:1920x1080@60  79:1920x1080@60  80:1600x1200@60  81:1680x1050@60  82:1600x900@60  83:1280x1024@60  84:1440x900@60  85:1280x800@60  86:1152x864@60  87:1280x720@60  88:1280x720@60  89:1280x720@60  90:1024x768@60  91:800x600@60  92:720x480@60  93:720x480@60  94:640x480@60  95:640x480@60  96:640x480@60  97:2560x1600@60  98:3200x1800@60  99:2880x1620@60  100:1368x768@60 
	Geometry: 1920,0 1920x1080
	Scale: 2
	Rotation: 1
	Overscan: 0
	Vrr: Automatic
	RgbRange: Automatic
	HDR: incapable
	Wide Color Gamut: incapable
	ICC profile: /home/chris/.config/color/icc/devices/display/LGUltraHD.icc
	Color profile source: ICC
	Color power preference: prefer efficiency and performance
	Brightness control: supported, set to 50% and dimming to 100%
	DDC/CI: allowed
	Color resolution: automatic (10), range: [8; 16] bits per color
	Allow EDR: unsupported
```