sentences:  Frank Popper, the eminent art historian, among others, commented on Palatnik's "luminous mobiles" and their aesthetic of motion.More recently, the term has been applied to the work of Ian Nunn, a Canadian computer scientist and artist who has done extensive work in the application of interference pigments and films to 2-dimensional painting surfaces.These special effect pigments, such as ChromaFlair, exhibit strong directional spectral reflectance and colour shifting with the angle of view.