Photographic film is a sheet of plastic (polyester, celluloid (nitrocellulose) or cellulose acetate) coated with an emulsion containing light-sensitive silver halide salts (bonded by gelatin) with variable crystal sizes that determine the sensitivity and resolution of the film. 
<Context ref.>Photographic film - Wikipedia, the free encyclopedia. [En línia]. [Consulta: 1 juny 2006]. Disponible a: <http://en.wikipedia.org/wiki/Photographic_film>