A method is provided of determining the cause of artifacts in images produced by an electrophotographic (EP) printer. A reference image is printed and artifacts in it are detected. After printing normal images, a test image is printed and artifacts in it are detected. If a detected artifact in the test image does not correspond to a detected artifact in the reference image, a characteristic frequency spectrum of the artifact in the test image is determined. Run-out on rotatable imaging components is measured, and a characteristic frequency spectrum of each is determined. The test image spectrum is compared to each component spectrum to identify which component is causing the artifact.