Specifications

Troubleshooting Symptom Charts/Screen Brightness - 6
Screen Brightness
Screen image dim 1 Adjust front panel brightness (it may be set too low).
2 Open the Monitors control panel and click Calibrate in the
Color menu to change the color calibration.
3 From the Monitors control panel, click Calibrate in the Color
menu and try changing the color calibration settings.
4 If screen brightness has decreased over time, the most likely
condition is the backlights failing. If you suspect backlight
failure, contact Apple Technical Support.