Install Brightness Indicator in Ubuntu 13.04
Add a brightness indicator to your Ubuntu 13.04 system
Here's how you can install a screen brightness indicator in Ubuntu 13.04.
1. Open a terminal window.
2. Type in the following commands then hit Enter after each.
sudo add-apt-repository ppa:indicator-brightness/ppa
sudo apt-get update
sudo apt-get install indicator-brightness
For more, see the original article at the link below.