In recent years electron transfer rates have been measured from excited dye molecules of both monomeric and J-aggregate form into silver halide crystals over a wide range of temperatures with picosecond time resolution. From these new experimental results, one obtains definite information about the energetics, electronic coupling strengths, and dynamic parameters of the reaction. These data can serve as the first basis for a detailed comparison and test of notions that have been advanced in the past to describe the relevant energetics and dynamics of the primary electron injection process into silver halide grains. The comparison will be made in particular with the models that have been widely used in the past by the photographic community, but also with the somewhat different concepts that have been developed for other closely related physical systems.