The paper leans on a movie cult from the 1960s, Blow-Up (1966) by Michelangelo Antonioni, of which a famous sequence is often mentioned, the one in which the protagonist, the photographer Thomas (considered here as a "conceptual character"), repeatedly enlarged the photographs he made in a park, in order to find an answer to the mystery surrounding the murder of a man: magnification which leads, on the one hand, to a gradual loss of definition of images, with the grain of (...) the picture becoming more and more evident, but also, on the other, in the emergence, from the very material of the print, of a fundamental detail that will help solve the mystery. What interests is the link between indicative referentiality and evidence documentary, between degrees of definition and authentication powers. The paper also analyzes the links that intertwine, in the film, between the photographs of Thomas (by Don McCullin) and paintings painted by another character of the movie, Bill (directed by Ian Stephenson), but also, outside the film, with all a series of examples from artistic production and visual culture of the time: very low definition images of the Kennedy assassination in Dallas (the famous Zapruder Film), the portrait of Lee Harvey Oswald directed by Sigmar Polke by simulating the halftone technique, the war photographs of Don McCullin and David Bailey's Fashion Photographs, Random Earths Studies by Mark Boyle and Joan Hills, Materialologies and Texturologies by Jean Dubuffet, as well as Zen for Film by Nam June Paik. Fimiani's text addresses also two contemporary installations which have tried to return to the issues from the photographic sequence of Antonioni's film: Blow-Up Blow-Up (2010) by Joan Fontcuberta and Portrait Landscape (from the Object Classifier series) (2015) by John Houck, an installation in which photograms of Blow-Up are analyzed through facial recognition software. (shrink)