The accuracy of lattice parameter determinations by Read camera x‐ray diffraction is shown to be strongly dependent on camera alignment. Alignment of the Read camera eliminates the main sources of error. Further improvement in analysis was achieved by constructing a collimator with a rectangular cross section. Analysis and testing showed that the rectangular collimator enhances the efficiency, resolution, precision, and peak‐to‐background intensity ratio for x‐ray analysis of thin films using the Read camera.