The Photographic Response of a Grain Size Series of AgCl Cubic Emulsions

Abstract

The photographic sensitivity of a series of sulfur-plus-gold sensitized AgCl cubic emulsions ranging in size from 0.29 to 3.14-μm (cube edge length) was established in a model color-forming single-layer format. Each emulsion was spectrally sensitized to green light with a single sensitizing dye. The measured sensitivity gains with increasing grain size fell considerably short of those expected from simple surface area per grain considerations, thus confirming the limited potential of AgCl cubic grain technology in exposure-limited photographic applications. An additional shortcoming of using increased grain volume to obtain increased sensitivity was evident by the six-fold decrease in maximum density exhibited through the thousand-fold grain volume change. As part of this study, a highaspect-ratio {100} tabular grain AgCl emulsion (1.94 × 0.14 μm) was included for comparative purposes. This tabular grain emulsion, when sensitized in a fashion similar to that of the cubic emulsions, yielded a photographic response consistent with increased surface area per grain and more in line with the expected dye speed versus grain surface area relationship of the cubes.