Abstract: A display device such as a projector and its adjusting system are provided which are arranged to easily adjust a brightness tracking (gamma) characteristic and a white balance of a displayed image. On the screen of the display device of the invention are displayed an image composed from a video signal, an adjustment item, adjustment patterns for aiding in gamma (white balance) adjustment and all the concerned adjustment values. The display device is arranged to execute the adjustments while the user is making sure of the adjusted states of a white area, a black area and a gray area therebetween. This arrangement thus allows the user to efficiently execute the adjustments according to his or her intended characteristic for a short length of time.