The high-intensity reciprocity failure (HIRF) in three silver bromide emulsions has been examined. The observation of Sauvenier and Hautot that sulfur-sensitized grains exhibit HIRF whereas unsensitized grains do not has been confirmed.
The HIRF of sulfur-sensitized grains appears to be a development phenomenon and is due to a wide distribution of the induction periods of the individual grains. Gold latensification greatly narrows this distribution of induction periods.
The onset of HIRF in the grains of the simple emulsion is accompanied by the onset of a Poisson distribution of development specks. Gold latensification increases the number of countable specks but does not change their distribution.
HIRF is a function of the surface concentration of sulfide ions. A low concentration produces sensitization but no HIRF, whereas higher concentrations produce HIRF. Gold latensification of the exposed grains before development usually removes HIRF. Extended development diminishes but does not remove HIRF.
It is postulated that sulfur sensitization may change either the localized silver-ion properties around the sulfide center on the grains, or the electronic properties of the grain.
H. E. SPENCER and R. E. ATWELL, "Sulfur Sensitization and High-Intensity Reciprocity Failure of Silver Bromide Grains," J. Opt. Soc. Am. 54, 498-505 (1964)