Some members of the group Nouvelle tendance (1961–1965) in Europe also were engaged in op art as Almir Mavignier and Gerhard von Graevenitz, mainly with their serigraphics. They studied optical illusions. The term "op" irritated many of the artists labeled under it, specifically including Albers and Stanczak. They had discussed upon the birth of the term a better label, namely "perceptual art". From 1964, Arnold Schmidt (Arnold Alfred Schmidt) had several solo exhibitions of his large, black and white shaped optical paintings exhibited at the Terrain Gallery in New York.