The brightness controls on my Lenovo ThinkPad W510 were not working at first. The display was stuck on a really bright setting which was tough on the eyes. I asked a user on UbuntuForums to help.
He showed me what to do, and recommended the ThinkWiki page for the W510.
Here is the fix:
sudo gedit /etc/X11/xorg.conf
Then add the following line at the bottom of the “device” section.
Option “RegistryDwords” “EnableBrightnessControl=1”