Amplitude contrast

The angular distribution of scattered intensities varies as a function of the atomic composition and density of the object. Electron opaque object points produce appreciable scattering through relatively large angles. Thus, many of the electrons incident on such points are excluded from the lens aperture and the intensity of the images of these points is correspondingly low. Conversely, electron transparent regions in the object, which are of lower average atomic number and/or thickness (mass density) produces little scattering beyond the lens aperture. The intensity of images of these points is correspondingly high.