An Incremental Photometer and Optical Measurements in the Photographic Latent-Image Range*

Abstract

An instrument for measuring very small changes in optical absorption has been designed and built. It operates with a constant narrow band of wavelengths and can be used for measuring changes in optical density of the order of 10⁻⁵. In a second instrument, spectrophotometric operation is attained with some sacrifice in sensitivity. The problems arising in this type of photometry are discussed. The instruments have been constructed primarily for the measurement of the print-out effect in silver halides. In selected photographic emulsions, this effect has been measured in the exposure range of latent-image formation.