Equivalent Quantum-Efficiencies of Photographic Emulsions

Abstract

Signal-to-noise equivalent numbers of stored photons and equivalent quantum-efficiencies are derived for four emulsion batches from homogeneous sensitometry and granularity data. The highest monochromatic efficiencies found are 0·9 per cent in the blue and 0·6 per cent in the red. Peak efficiencies occur at densities of only 0·1 to 0·2 above fog. The peak equivalent number of photons stored ranges from 0·03 per $${\mu }^{2}$$ for the “ fastest ” emulsion in the blue to 0·4 per $${\mu }^{2}$$ for the finest grained material in the red. The distinction between exposure for maximum efficiency and for maximum equivalent storage is emphasised.