Increased Detectivity By Low Gamma Processing

Allan Shepp; William Kammerer

doi:10.1117/12.946793

1 April 1969 Increased Detectivity By Low Gamma Processing

Allan Shepp, William Kammerer

Proceedings Volume 0016, Image Information Recovery; (1969) https://doi.org/10.1117/12.946793
Event: Image Information Recovery, 1968, Philadelphia, United States

Abstract

Here and in other laboratories it has been observed that films exposed to subjects of an extended brightness range, processed in low gamma developers, show imagery of improved resolution and reduced flare in the normally overexposed region, and of generally improved visual fidelity over most of the exposure range, compared to the same exposure processed in a high gamma more active developer, although with a loss of toe speed and perhaps of pictoral quality. It has been generally assumed that since high gamma processing increases the contrast of the final image, it would not be possible to obtain improved imagery from low gamma processing. We explain the improved imagery of low gamma development in part by the effects of reduced density and increased contrast in the high exposure region, but principally by the fact that low gamma development leads to lower granularity and increased detectivity over most of the exposure range, compared to higher gamma development. We review detectivity and quantum efficiency theory and show that the ratio Rel d = y/σ (D, A) as a function of exposure, is the detectivity parameter of interest, since the ratio of Rel d for any two conditions of processing is the ratio of quantum efficiencies and of detectivities.

Citation Download Citation

Allan Shepp and William Kammerer "Increased Detectivity By Low Gamma Processing", Proc. SPIE 0016, Image Information Recovery, (1 April 1969); https://doi.org/10.1117/12.946793

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