Op art is a term used to described certain paintings made primarily in the 1960s which exploit the fallibilty of the eye through the use of optical illusions.
Op art works are usually abstract, with many of the better known pieces made in only black and white. When the viewer looks at them, the impression is given of movement, flashing and vibration, or alternatively of swelling or warping.
The term first appeared in print in Time Magazine in October 1964, though works which might now be described as "op art" had been produced for several years previously. It has been suggested that Victor Vasarely's 1930s works such as Zebra (1938), which is made up entirely of diagonal black and white stripes curved in a way to give a three-dimensional impression of a seated zebra, should be considered the first works of op art.
In 1965, a show called The Responsive Eye, made up entirely of works of op art, was held in New York City. This show did a great deal to make op art prominent, and many of the artists now considered important in the style exhibited there. Op art subsequently became tremendously popular, and op art images were used in a number of commercial contexts. Bridget Riley tried to sue an American company, without success, for using one of her paintings as the basis of a fabric design.
Bridget Riley is perhaps the best known of the op artists. Taking Vasarely's lead, she made a number of paintings consisting only of black and white lines. Rather than giving the impression of some real-world object, however, Riley's paintings frequently give the impression of movement or colour.
Riley later produced works in full colour, and other op artists have worked in colour as well, although these works tend to be less well known. Violent contrasts of colour are sometimes used to produce similar illusions of movement.
Other noted op artists include Jesús-Rafael Soto and Richard Anuszkiewicz.