From the study of the distribution of latent images and the Sabattier effect of emulsions with internally sensitized core–shell grains having uniform iodide distribution, it is found that the surface sensitivity decreases with increase of the internal sensitivity. To show a strong Sabattier effect, an emulsion should contain grains with both surface sensitivity centers and internal sensitivity centers, and they should be well matched. The ratio of the two sensitivities and the second exposure are two important factors that decide the kinds of Sabattier reversal. The results can be explained by the behavior of photoelectrons and photoholes within the silver halide grains during the two exposures and developments. The surface latent image specks formed during the first exposure are bleached by the photoholes during the second exposure, resulting in a reversed image.
Jian-bin Hu, Si-yong Zhuang, Jian-ping Wu, "Sabattier Effect in Internally Sensitive Emulsions" in Journal of Imaging Science and Technology, 1996, pp 229 - 232, https://doi.org/10.2352/J.ImagingSci.Technol.1996.40.3.art00007