The role of silver clusters in photography

The principle of silver photography is based on the photosensitivity of minute silver halide crystals. The light generates clusters of a few silver atoms on the crystals. Their ensemble constitutes the latent image of extremely weak intensity and invisible. The development consists of converting chemically into metal particles the crystals containing a cluster with a supercritical number of photoinduced silver atoms and of transforming catalytically the latent image into a visible picture. Crystal doping by a selective anti-oxidant scavenger permits one to avoid the loss of electrons, which otherwise recombine rapidly with holes, and to reach the integral quantum yield of atoms produced per photon absorbed. To cite this article: J. Belloni, C. R. Physique 3 (2002) 381–390.