The process works by using means of an optical illusion. Traditionally (as opposed to stochastic screening), a fixed number of small dots of varying size are printed at specific angles for each color. The size of the dots controls the amount of a particular color that is reproduced. By mixing the four colors (magenta, yellow, cyan and black), it is possible to reproduce a large enough spectrum of colors to make the viewer believe what he is seeing is a continuous tone, color image.