SUMMARY Often one or both of my monitors have very low brightness on session start. STEPS TO REPRODUCE 0. Use Wayland. 1. Log in to a session from SDDM. 2. If monitors have normal brightness, log out and go to 1. OBSERVED RESULT One or both monitors have very low brightness. SOFTWARE/OS VERSIONS Operating System: Arch Linux KDE Plasma Version: 6.2.0 KDE Frameworks Version: 6.7.0 Qt Version: 6.8.0 Kernel Version: 6.11.3-arch1-1 (64-bit) Graphics Platform: Wayland Processors: 16 × Intel® Core™ i9-9900K CPU @ 3.60GHz Memory: 31.1 GiB of RAM Graphics Processor: NVIDIA GeForce RTX 3090/PCIe/SSE2 Also, this is a desktop system with two monitors connected. ADDITIONAL INFORMATION 1. Started once I updated to KDE 6.2. 2. I could not reproduce it on X, only happens on Wayland. 3. This is NOT likely related to ddcutil - the value it sets matches the value I see in monitor. Unfortunately I have not found a way to correct the problem even after logging in, except to log out and log in again, or reboot, and hope for the best. I am unsure if it is an issue with powerdevil, but brightness appears to be related to it?
More info: Once logged in, enabling / disabling / disconnecting / reconnecting monitors don't appear to make a difference. However logging out and logging in again appears to reroll the dice on whether brightness will be low this time.
NVidia Version: nvidia-560.35.03-13
I have same issue + "Power Management -> Change screen brightness" does not have any effect. Command to set screen brightness to 40% works: sudo ddcutil setvcp 10 40 SOFTWARE/OS VERSIONS Operating System: openSUSE Tumbleweed 20241013 KDE Plasma Version: 6.2.0 KDE Frameworks Version: 6.7.0 Qt Version: 6.7.3 Kernel Version: 6.9.9-1-default (64-bit) Graphics Platform: Wayland Processors: 12 × AMD Ryzen 5 5600U with Radeon Graphics Memory: 38,0 GiB of RAM Graphics Processor: AMD Radeon Graphics Manufacturer: LENOVO Product Name: 20X70042CK System Version: ThinkPad L15 Gen 2a
For me, the lower brightness remains even with `ddcutil setvcp 10 30`. I can see brightness change with `ddcutil setvcp 10 40`, but the overall brightness still remains low. It's as if there is something else independently changing the brightness of the screen, on top of ddcutil, only when KDE session is active.
AFAICT, this is related or directly caused by this SDDM bug - https://bugs.kde.org/show_bug.cgi?id=494894 I am not sure why, but probably SDDM has some kind of overlay which continues to persist. Reason for believing that is the fact that once I switched to ly, I did not see this problem again so far.
I'm seeing similar, but for me it happens after logging in from screen-lock, possibly after laptop was suspended (but not always). Usually it's both monitors (laptop and external), and the Brightness sliders usually match the actual brightness. But today, for example, both monitors were dim, the laptop slider was at 0%, but the external slider was at 100%. So the external slider position did not match the actual monitor brightness. When I moved the sliders, each monitor reacted correctly. So far, moving the sliders always corrects the problem for me. It would be useful if a dev could suggest some things to check to help with diagnosis. Is there something in syslog? Something to check in dbus?
Forgot to paste this: Operating System: KDE neon 6.2 KDE Plasma Version: 6.2.0 KDE Frameworks Version: 6.6.0 Qt Version: 6.7.2 Kernel Version: 6.8.0-47-generic (64-bit) Graphics Platform: Wayland Processors: 8 × Intel® Core™ i7-10610U CPU @ 1.80GHz Memory: 15.3 GiB of RAM Graphics Processor: Mesa Intel® UHD Graphics Manufacturer: LENOVO Product Name: 20UCS4TR00 System Version: ThinkPad X1 Yoga Gen 5
I have disabled sleep, hence I will miss if resuming from sleep also causes this, but sounds similar otherwise. IIRC resume reopens SDDM to log back in. If so it could still be an issue with SDDM.
This sounds like a bug I'm experiencing. My screens are very dim on Wayland, normal brightness on X and on SDDM, rebooting doesn't seem to solve anything. Kernel: 6.11.5-gentoo-dist Nvidia drivers: 565.57.01 I can increase the brightness to some extent using ddcutil set to 100 but it's still pretty dim. kscreen-doctor always reports my brightness at 30% and changing it has no affect on what is reported in kscreen-doctor -o. HDR is disabled, I've tried with variable refresh on and off.
Operating System: CachyOS Linux KDE Plasma Version: 6.2.4 KDE Frameworks Version: 6.8.0 Qt Version: 6.8.0 Kernel Version: 6.12.1-1-cachyos-autofdo (64-bit) Graphics Platform: Wayland Processors: 16 × AMD Ryzen 7 5800X 8-Core Processor Memory: 31.3 GiB of RAM Graphics Processor: AMD Radeon RX 7800 XT On waking from sleep brightness will drop to 30% - for me this seems to be the only condition that causes the brightness drop. Default settings used in Power Management though I've tried different settings in the past so I'm pretty sure it's nothing to do with Power Management. Desktop system powered via UPS.
Re. original issue (Comment #0) filed by Arnab Bose: I believe this was a symptom of KWin/Wayland using either hardware brightness or software brightness adjustments, depending on what's available. It would work like this: 1. Hardware brightness controls are available for your screen, you set it to e.g. 50%, then restart your session. 2. Hardware brightness controls somehow aren't getting initialized correctly, but the screen is still at 50% hardware brightness. However, KWin doesn't know about hardware brightness now, so it uses software dimming to reduce brightness to 50%. Combined with the existing hardware brightness, this makes for only 25% and explains why e.g. ddcutil won't restore brightness back to to 100% in that session. This was fixed in KWin by https://invent.kde.org/plasma/kwin/-/merge_requests/6670 which was first released with Plasma 6.2.3. Not sure if we had a bug report or which one it was, I'll just close this as fixed. If the original reporter (Arnab) still experiences this issue, please reopen this bug with a status update of how your system is behaving now. --- Oliver's dimming issue from Comment #10 is likely a different bug, which would be fixed by https://invent.kde.org/plasma/powerdevil/-/merge_requests/466 (and related MRs), shipping to users from Plasma 6.3 Beta 1 onwards. I'll regard this as unrelated to the original report. Please open a separate bug if you still find issues with this in Plasma 6.3. Thanks!
Thank you - I have switched to `ly` about 2 months ago when I faced this issue, and have not seen it since then. The reason for switching was this issue. So I thought it might have had something to do with how SDDM works, as I mentioned in Comment #5. This also correlates to the fact that the problem - at random after each KDE login from SDDM - occurred only at log in and stayed the entire session. I don't clearly remember but it is possible that at the same time I also updated and received the patch in https://invent.kde.org/plasma/kwin/-/merge_requests/6670, and that was the real fix.