When your laptop computer is running on battery, the screen will dim when the computer is idle in order to save power.
You can adjust the dimming brightness, disable it, or change the amount of time before dimming by following these steps:
Click
Type gconf-editor. The
In the left panel click
In the right panel, you can now adjust the
You can also choose to disable this feature by unchecking the box next to
Explain that screen dimming is a power saving feature, normally when disconnected from AC power. Link to power-dim to explain how to control this behaviour.