Much of the learning to practice as well as to appreciate art is concerned with understanding the basic principles. One of these principles is what Harold Speed calls "dither," the freedom that allows realism and the artistic vision to play against each other. Very important to any artist or work of art, this quality separates the scientifically accurate from the artistically accurate. Speed's approach to this problem is now considered a classic, one of the few books from the early years of this century that has continued to be read and recommended by those in the graphic arts.