Electron diffraction is an essential characterization tool for materials scientists. When using the transmission electron microscope (TEM) to perform diffraction experiments, setting up the microscope for both calibration standards and unknown materials in a consistent method ensures that dependable results are obtained. Care must also be exercised to protect digital cameras from intense transmitted and diffracted beams to avoid damage. In Parts 1 and 2 of this series, procedures were presented for recording high-quality, well-calibrated, digital SAED patterns. In Part 3, aspects of diffraction analysis software packages and the reliability of data are discussed.