Screen brightness control limited to narrow range after screensaver turns on - Lenovo t430s

Hi everyone,

I’ve just installed 12.3 (KDE) and have been busy setting everything up just the way I want it for the last few days. Very happy to be back to Linux, and to venture outside the Debian/Ubuntu lineage for the first time. I’m impressed!

I’m having a problem with the brightness control. It works just fine when I first boot my machine, a Lenovo t430s, but when I unlock the screensaver, the brightness keys still work, and the on-screen display comes up, but it only lets me adjust the brightness from 25% up to 65% according to its scale. It also looks like it’s not turning the brightness up or down all the way; 25% to 65% looks about right.

I’m not sure whether this problem was there before I started installing software, or whether it’s something new. What I have noticed is that, when it is working properly, the brightness keys increase/decrease in even increments of 10%. (20%, 30%, 40%…) It’s only when it isn’t working properly that I see increments of 10% ending in 5. (25%, 35%, …)

I’m not sure where to start looking for log information that might help, so if you could point me in the right direction, I’ll post a more useful description of the problem.



Add the following kernel parameter to the GRUB_CMDLINE_LINUX_DEFAULT=”quiet splash” line. The directory is /etc/default/grub

acpi_osi="!Windows 2012"

Reboot your laptop.