To provide a display device capable of displaying a moving picture with high definition and at high speed. An image display system includes: an image display unit; and a control unit. The control unit has: a block discrimination circuit portion; an image processing portion; a storage portion; and a synchronizing signal generation portion. The block discrimination circuit portion discriminates a moving picture or a still picture to process the image information in accordance with the discriminated result, in which the number of gradations for the image information processed when the discriminated result is the moving picture is lower than when the discriminated result is the still picture. Thereby, the high definition image display and the high speed moving picture display can be effected by reducing the information with lower degree of recognition.