This article analyses Blow Up, Michelangelo Antonioni´s film, so as to understand how its visual discourse questions the relationship between the real and the imaginary. Behind a crime we know nothing about and will never know, the search carried out by the photographer reveals and questions the relationships between the images and the things whether photographs or films. He proposes meanings for their foundations and points of view, that set them apart from interpretations that see them as reproductions or representations of a a real presupposed as being whole and pre-existent.