An electronic device for controlling a brightness of a light source and an operating method of the electronic device are provided. According to the electronic device and the operating method, an image including an ambient environment of a light source is captured, information of an exposure of the captured image is obtained, information about a brightness of the ambient environment of the light source is determined based on the information about the exposure, and a brightness of the light source is controlled based on the determined information about the brightness of the ambient environment.