Latent image internal

Internal latent image is a latent image formed inside the grains. It can be developed by a conventional developer to which is added a silver halide solvent or an agent that promotes recrystallization of the silver halide to allow the developer to make contact with the latent image centers. 

The photographic attributes of (S+Au)-sensitization are similar to those of S-sensitization. Both act primarily to increase the sensitivity for surface image formation. Both usually decrease the sensitivity for internal latent image formation in emulsions that show considerable internal sensitivity in their unsensitized form. Bahnmueller (163) and Farnell and Solman (164) observed that, in emulsions of this type, the combined (S+ Au)-sensitization produced a greater increase in surface sensitivity and a greater decrease in internal sensitivity than S-sensitization alone, but sensitization with gold alone increased surface sensitivity without impairing the internal sensitivity (163). 

Iridium salts are of current interest as sensitizers for internal latent image formation (189,190). The iridium ions are incorporated in the grains during their preparation, probably as a complex associated with silver ion vacancies. 

The nuclei form both at the surface and in the interior of the cry tal, but the theory developed by Mott (49) assumes that the defects are interstitial Ba - ions and that the nuclei grow at the surface of the grains only. As in the formation of the latent image in sensitized Ag halide grains, the assumption of pure Frenkel defects could only lead to the formulation of surface nucleation, but recent developments have led Mitchell to consider the role of Schottky defects (F-centres), which may forn internal aggregates ultimately bi caking away from the parent lattice as minute nuclei of the new metal phase. It is possible that a similar state of affairs exists in azides (36) unfortunately, nothing is known of the nature of... 

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