I am not able to control the brightness of the screen fully via Fn/Home and Fn/End on a ThinkPad X220. It will not let me turn the brightness off entirely or up to 100%, and also the the screen brightness doesn't fade up and down smoothly but in flashing jumps.
Is there a way that settings can be reset, perhaps?
/Nicolai
Hey 
How about if you are locking / unlocking fn keys with fn + escape and try again ?
You can also try to force use or not to use fn keys inside the bios (fn lock)
Hey - thanks for your reply
fn+esc does not seem to work 
I tried to change the bios settings, but that doesn't really make any difference.
Another funny thing is that when I try to turn brightness all the way up with the keyboard, it only reaches to 76%, and similarly when I try to turn it all the way down, it does in fact show 0%, but the screen is only dimmed - not turned all off. Very strange. I can turn it all up and all of with the slider in the Brightness Applet in the system tray, which is why I wonder if this could be a setting that needs to be removed and/or reset?
Hi back
I would try to upgrade the kernel to a new version
You can do it with Mainline - easy and good working
Hi again
Update 
I think my problems with the keyboard-controlling of the brightness of the display might have something to do with the firmware version, since I have two other x220's with firmware versions from 2018, and the work quite well. The one making problems is updated in 2011. I don't know if this is just a coincidence - it would be a funny one...