Lenovo Y400 ubuntu 12.04 can't change brightness

Question

The ubuntu seems to be always on the max brightness.

I cannot change the brightness. Really strange.

What I have tried:

1 Install the latest Nvidia Driver does not work

2 change x

sudo gedit /etc/X11/xorg.conf

Section "Device"
Identifier    "Default Device"
Driver    "nvidia"
Option    "NoLogo"    "True"
Option "RegistryDwords" "EnableBrightnessControl=1"
EndSection 

This would make the fn+ key successfully change the value of /sys/class/backlight/acpi_video0/brightness and actual_brightness

However the brightness will still stay the maximum.

Answer 1

I have the same problem. Finally I found a method to solve it by using xrandr in this page (but the fn + up/down still cannot be used).

1. First get the output name entering the code below in terminal:
   xrandr -q | grep " connected"
   
   Then I get the result:
   LVDS-0 connected primary 1366x768+0+0 (normal left inverted right x axis y axis) 310mm x 174mm
   
   My output name is LVDS-0.
   
2. Then try to change brightness: (use your output name)
   xrandr --output LVDS-0 --brightness 0.8
   
   Then the brightness of my laptop becomes 80%.
   Hope this will help you.