A display device compresses light-emitting display of modifiable display luminance; a light sensor for detecting the surrounding brightness; and a control for adjusting the display brightness of the light-emitting display in response to a brightness value based on detected results of the brightness sensor. If absolute value of the difference between current and previously determined brightness values is less than a prescribed threshold value, the control determines that there is no change in brightness otherwise the central determines that there has been a change in brightness. Upon a determination of a predetermined number of times that a brightness change has occurred, the display luminance is adjusted in response to the current brightness value.