The cross section of the diffracted beam may or may not be identical to the one of the incident beam. In the case of strongly asymmetric reflections, the beam size (in the diffraction plane) is considerably expanded or compressed, with expansion occurring if the incidence angle is much smaller than the exit angle, and vice versa. Independently of this beam expansion, the relation of sample size to image size is given by the exit angle alone: The apparent lateral size of sample features parallel to the exit surface is downscaled in the image by the projection effect of the exit angle.