OS X Mountain Lion: Adjust your display’s brightness
If the images on your display are too light or too dark, you can adjust the display’s brightness.
- Use the brightness control keys. On portable computers, and if you’re using an Apple LED Cinema Display, they’re usually the F1 and F2 function keys. On some computers, they’re the F14 and F15 function keys.
- If you have a computer with ambient light sensing, choose Apple menu > System Preferences, click Displays, and then click Display. Select the option to turn on ambient light sensing.
The display automatically adjusts its brightness to match the current lighting level.
- Choose Apple menu > System Preferences, click Displays, and then click Display. Drag the Brightness slider to adjust the brightness of your display.
- Check the documentation that came with your display to find out how to control its brightness.
Depending on the type of display connected to your computer, the Display pane of Displays preferences may contain a Contrast slider that you can use to adjust the display’s contrast.