Using empirical relations established in the study of electron diffraction patterns of uniform thin films of aluminum, the contrast between the most intense ring and the background is calculated for other morphologies as a function of the accelerating voltage on the camera.In all cases the contrast increases with voltage. The gain is marked if the specimen is nowhere very thick. For specimens that have very thick regions the contrast increases approximately as the square root of the voltage in the range 50 to 150 kv. The situation in reflection‐diffraction in general lies between these extremes. Increasing the voltage has a more limited effect on increasing the range of specimen thicknesses that can be examined than had been previously supposed.