Summary: we need is a way to characterize printers with enough accuracy to achieve useful results only the most exacting of professional printers will need to measure their output photometrically A step in this direction is possible with the aid of an image that contains all 256 possible gray levels Here s an image of gray squares that includes all the values from 1 to 255 which is
Image Dimensions: 555 x 629
Image originally found here.