The Density Contribution per Developed Grain and the Effect of Size Spread on the Granularity of Film Coatings^*

* The following acronyms are used to describe the couplers: DIR= Development Inhibitor Releasing, DIAR=Development Inhibitor Anchimeric Releasing (where DI(A) is used here to indicate both types), BARC=bleach accelerator releasing coupler.

Abstract

The mean density contribution per developed grain is estimated from measurements of number of developed grains and of dye density for coatings of emulsions containing image couplers and combinations of image and DI(A)R couplers. The density contribution per developed grain urns constant with density for all the image couplers examined but did show a fall towards higher densities for some D1(A)R couplers. These data were used to calculate the dye granularity which was always lower than the measured values due to the size spread of the developed silver and dye clouds.

The effect of the size spread on the proportion of the developed grain population that effectively contributes to the granularity was investigated by measuring the size spreads of processed emulsions and by modelling the behaviour using a log-normal distribution. It is postulated for a typical size spread that 40% of the developed grains produce 95% of the granularity and that the remaining grains may contribute to density but they have an insignificant effect on the granularity or graininess.

Notes

* The following acronyms are used to describe the couplers: DIR= Development Inhibitor Releasing, DIAR=Development Inhibitor Anchimeric Releasing (where DI(A) is used here to indicate both types), BARC=bleach accelerator releasing coupler.