Changing monitor brightness programatically in Ubuntu 11.10

Question

I'm using Dell inspiron 1564 laptop with Ubuntu 11.10. Here I can change my monior brightness simply via fn+F4/5. But I need a low brightness even lower than the min limit of fn+F4. How can I do it programatically or which shell command to use for that?

Answer 1

I'm not sure that it's possible to go lower than what the laptop controls get you, but you can programatically change brightness by echoing a value to /sys/class/backlight/<something>/brightness. On my netbook the 'something' is acpi_video0.

$ cat /sys/class/backlight/acpi_video0/brightness
10
$ sudo sh -c 'echo 0 > /sys/class/backlight/acpi_video0/brightness'
$ cat /sys/class/backlight/acpi_video0/brightness
0

Edit: There's also xbacklight, which uses XRandr.

Answer 2

According to this site, you should be able to alter the brightness by modifying the /proc/acpi/video/VGA/LCD/brightness file.

The valid brightness levels appear to be:

levels:  12 25 37 50 62 75 87 100

So modifying that file accordingly should do what you need.

Answer 3

you can change it by following command sudo setpci -s 00:02.0 f4.b=00, here you can enter value from 00 to ff in hexadecimal, [00 = bright and ff = dull]

for more details go through the following link : http://daksh21ubuntu.blogspot.in/2011/12/how-to-increasedecrease-brightness-on.html