Figure 12. Laser printer artefact. This oblique foot image demonstrates two different artefacts. The fine white line (black arrow) running parallel with the long dimension of the film is an artefact from the laser printer. The line running perpendicular to the long dimension of the film (white arrow) is caused by dirt on the light guide of the photomultiplier tube in the plate reader, as in Figure 5. Artefact remedy: service personnel can use a camel hair lens brush to clean the mirror.