13.10 Can't Adjust Dell Laptop Backlight

Doing both of the steps mentioned here fixed this issue with a Dell Studio 1558 and Ubuntu 13.10: http://ubuntuforums.org/showthread.php?t=2181534

Change /etc/default/grub

I used "sudo vim /etc/default/grub" but use whatever editor you're comfortable with but you will need to use sudo to edit it as the root user.

From:

GRUB_CMDLINE_LINUX="acpi_backlight=vendor"

To:

GRUB_CMDLINE_LINUX=""

Then run:

sudo update-grub

Add /usr/share/X11/xorg.conf.d/20-intel.conf

I used "sudo vim /usr/share/X11/xorg.conf.d/20-intel.conf" and then ran :set paste and hit i for insert and pasted in the contents.

Section "Device"
    Identifier  "card0"
    Driver      "intel"
    Option      "Backlight"  "intel_backlight"
    BusID       "PCI:0:2:0"
EndSection

Then reboot and login again and your function key with the brightness up/down should work again.

Try this in a terminal:

echo 4000 | sudo tee /sys/class/backlight/intel_backlight/brightness

4000 is the full brightness, and 0 is no brightness (screen completely dark), so you can choose any value in between as you like. Note that the path to the brigtness may be different on your computer, so adjust accordingly.

This works for me on Dell Studio 1558, Ubuntu 13.10 64 bit. Also you'll have to do this every-time you have to change brightness. It will reset when you restart the computer.

Good luck!