The disclosure describes a system and method for controlling a light for a component of an electronic device. An embodiment uses brightness evaluation zones and progresses through one or more of the zones to determine whether and when to activate the light for given conditions of ambient light. In doing so, the embodiment sets a current brightness evaluation zone for the device and sets an activation status of the light level to an activation value associated with the current brightness evaluation zone. The embodiment compares an ambient light level for the device to the current brightness evaluation zone. Evaluation loops are provided to test and change the current brightness evaluation zone against the detected ambient light. The light may be a backlight.