Panoramic focal trough dimensions affect both the number of patient structures seen in radiographs and the margin of error possible when positioning a patient to take a radiograph. This study compares the dimensions, or size, and position, or form, of the focal troughs of four machines by resolution measurements. There is a continued need for technicians to position the patient's anterior teeth accurately in the zones of sharpness of these machines, but the widths of the sharpness zones show an increase in dimensions over older panoramic machines.