In the 1960s Dalí became particularly concerned with recherches visuelles -- explorations of the optical mechanisms of illusion and the perception of images. One line of research was in the construction, using systems of dots, of works with hidden images such as Portrait of my dead brother of 1963. (All his life Dalí was conscious of the brother, also called Salvador, who had died nine months before his own birth.) (op. cit., exh. cat., Paris, 1979, p. 20)

In Portrait de mon frère mort, Dalí uses Ben-Day dots to describe the main features of his brother's face. In some parts these dots glisten like droplets of liquid, elsewhere they merge to form tiny human figures, all set against the backdrop of an eerie desert landscape. This work is similar in execution to Dalí's earlier La Madone Sixtine (Museum of Modern Art, New York), in which what initially appears to be an abstraction of dots is transformed into Raphael's Sistine Madonna when viewed from two meters, and becomes a huge angelic ear at a distance of about fifteen. In both of these works, Dalí appears to have been influenced by photography. As in a photograph, forms which at first seem unified dissolve under close inspection into smaller, separate parts, which in turn reveal themselves as the actual particles that constitute the whole. Although artists such as Sigmar Polke and Roy Lichtenstein also began to experiment with dot paintings in the sixties, Dalí's ability to create so many levels of illusion was quite unparalleled at this time.