The image display system forms an image by scanning with light from a light source of a luminaire. The image display system includes: an input unit configured to receive an image signal indicative of an instruction value of luminance of the light source; and a control unit configured to determine a target value of luminance of the light source based on the instruction value indicated by the image signal received by the input unit. The control unit is configured to perform an adjusting process of setting the target value to an adjusted value different from the instruction value when allowing the light source to emit light based on the image signal.