When I use my function key to adjust brightness the computer freezes. I tried to use xbacklight but that has no effect.
oli@oli-Lenovo-G580:~$ xbacklight -get
100.000000
oli@oli-Lenovo-G580:~$ xbacklight -set 110
oli@oli-Lenovo-G580:~$ xbacklight -get
100.000000
oli@oli-Lenovo-G580:~$ xbacklight -set 90
oli@oli-Lenovo-G580:~$ xbacklight -set 50
oli@oli-Lenovo-G580:~$ xbacklight -get
50.000000
oli@oli-Lenovo-G580:~$ xbacklight -set 100
oli@oli-Lenovo-G580:~$ xbacklight -set 10
oli@oli-Lenovo-G580:~$ xbacklight -get
10.000000
oli@oli-Lenovo-G580:~$ xbacklight -set 11
oli@oli-Lenovo-G580:~$ xbacklight -set 1
oli@oli-Lenovo-G580:~$ xbacklight -get
0.000000
oli@oli-Lenovo-G580:~$ xbacklight -set 100
oli@oli-Lenovo-G580:~$
had no noticeable effect on my screen brightness.