ABSTRACT
The foundation of silver-based photography is the light sensitivity of silver salts named silver halides: the chloride, bromide and iodide salts. The extent to which an emulsion has been dye sensitized makes a considerable difference to the amount and quality of light that is permissible during manufacture and in processing. Silver salts are usefully light sensitive, or can be made so by spectral sensitization. They are also developable to amplify the invisible effect of small exposures the photographic latent image. If the excited electron can pass from the dye to the crystal, latent image formation may proceed. Infrared materials find use in aerial photography for haze penetration and for distinguishing between healthy and unhealthy vegetation, in medicine for the penetration of tissue, in scientific and technical photography for the differentiation of inks, and fabrics, which appear identical to the eye, and in general photography for pictorial effect.
