Reciprocity (photography) - Quantum Reciprocity-failure Model

Quantum Reciprocity-failure Model

Modern models of reciprocity failure incorporate an exponential function, as opposed to power law, dependence on time or intensity at long exposure times or low intensities, based on the distribution of interquantic times (times between photon absorptions in a grain) and the temperature-dependent lifetimes of the intermediate states of the partially exposed grains.

Baines and Bomback explain the "low intensity inefficiency" this way:

Electrons are released at a very low rate. They are trapped and neutralised and must remain as isolated silver atoms for much longer than in normal latent image formation. It has already been observed that such extreme sub-latent image is unstable, and it is postulated that ineffiency is caused by many isolated atoms of silver losing their acquired electrons during the period of instability.

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