Internal-Image Formation and Related Photographic Effects

In accordance with generally accepted views, it is shown that variations in degree of Clayden and Villard effects and in Solarizability can be broadly correlated with the surface/internal speed ratio. In particular it is shown that increase of surface/internal speed ratio by increase of digestion time, or simply by increase of exposure time, leads to a decrease in the Villard effect, and that solarizability can be greatly enhanced by kinking which increases internal sensitivity without much effect on surface response. However, among collections of commercial emulsions, correlations between surface/internal speed ratio and latent-image effects involving rehalogenation processes are masked by differences in the halogen-accepting properties of the emulsions. Observations on the Villard effect support the view that the grains which do not form surface image readily are the more sensitive ones for internal-image formation, and this should be recognised in attempting to deduce ratios of surface to internal speed.