Dell U2412M User Manual page 20

Brightness Brightness adjusts the luminance of the backlight.
Push the button to increase brightness and push the
NOTE: Manual adjustment of Brightness is disabled when Energy Smart or Dynamic Contrast is switched on.
Contrast Adjust Brightness first, and then adjust Contrast only if further adjustment is necessary.
Push the button to increase contrast and push the
The Contrast function adjusts the degree of difference between darkness and lightness on the monitor screen.
Auto Adjust Even though your computer recognizes your monitor on startup, the Auto Adjustment function optimizes the display settings for use with your particular setup.
Auto Adjustment allows the monitor to self-adjust to the incoming video signal. After using Auto Adjustment, you can further tune your monitor by using the Pixel Clock (Coarse) and Phase (Fine) controls under Display Settings.
NOTE: In most cases, Auto Adjust produces the best image for your configuration.
NOTE: Auto Adjust option is only available when you are using the analog (VGA) connector.
Input Source Use the Input Source menu to select between different video signals that may be connected to your monitor.
button to decrease brightness (min 0 ~ max 100).
button to decrease contrast (min 0 ~ max 100).