The basic parameters of print quality are resolution, addressability, gray scale, and dot microstructure. A real device also has intrinsic variability in the printing process, producing visual artifacts, which come under the general heading of noise. Some of the more common manifestations of this are background scatter, dot placement errors, voids (due to nozzle malfunction in ink jet, for example), and banding in images. The significance of any of these aspects of print quality can only be determined by examining them with respect to the properties of the human visual system. The design choices of the basic print quality parameters are, therefore, guided by the properties of the human visual system to determine where improvement needs to be made or where little is to be gained by increasing any one of the specifications.