Hold , and select Settings > System > Backlight.

Mode

Sets the backlight to turn on for interactions which includes the keys, touchscreen, and notifications. The device has an ambient light sensor that detects the light level. Interactions activate the backlight in a low-light environment. Gestures include rotating your wrist toward your body to view the device.

Timeout

Sets the length of time before the backlight turns off.

Brightness

Sets the brightness level of the backlight. During an activity, the backlight uses the brightest setting.