A major development in the 1960s of painting that created optical effects for the spectator. These effects ranged from the subtle, to the disturbing and disorienting. Op painting used a framework of purely geometric forms as the basis for its effects and also drew on colour theory and the physiology and psychology of perception. Leading figures were Bridget Riley, Jesus Raphael Soto, and Victor Vasarely. Vasarely was one of the originators of Op art. Soto's work often involves mobile elements and points up the close connection between Kinetic and Op art.