The Settings charm is the user’s primary interaction point for setting the display brightness.
After selecting Settings charm, the user can invoke the brightness change slider by tapping down or clicking on Screen. Dragging the slider up or down adjusts the display brightness: moving up brightens the screen, moving down dims the screen. Figure 1 Using Settings Charm to change brightness shows the steps. Brightness changes that are made through this interface persist across system power transitions (for example, sleep and restart), and effectively overwrite the brightness level for the current power mode (plugged-in or on-battery).
Figure 1 Using Settings Charm to change brightness