Hungarian-born painter who became a French citizen in 1959, the main originator and one of the leading practitioners of Op art. He settled in Paris in 1930, and for the next decade worked chiefly as a commercial artist, particularly on the designing of posters, showing a keen interest in visual tricks such as trompe-l'œil effects. From 1943 he turned to painting and about four years later he adopted the method of geometrical abstraction for which he was best known. Typically he created a hallucinatory impression of movement through visual ambiguity, using alternating positive–negative shapes interrupted in such a way as to suggest underlying secondary shapes. His fascination with the idea of movement led him to experiment with Kinetic art and he also collaborated with architects in such works as his relief in aluminium for Caracas University (1954) and the French Pavilion at ‘Expo '67' in Montreal, hoping to create a kind of urban folk art. From the mid-1950s he wrote a number of manifestos, which, together with his paintings, were a major influence on younger artists working in the same fields. Among them is his son Jean-Pierre (1934– ), who works under the name Yvaral.