Abstract: An X-ray spotfilming apparatus including a film cassette carriage mounted for longitudinal, reciprocating motion in housing having at least one film cassette receiving opening. A carriage drive system including a servomotor and a feedback potentiometer is operative to drive the film carriage between a retracted position and a plurality of exposure positions. Clamp members are mounted for sliding transverse movement within the carriage assembly and are operative in connection with a clamp coupling mechanism and clamp drive system to effect both clamping and translational movements within the carriage. A cassette advance apparatus drives a film cassette to a predetermined position along a clamp members and includes a advance pawl engageable with the cassette and a feedback pot for monitoring the position of the pawl. The feedbck signals from the clamp drive and cassette advance potentiometers are utilized to determine the longitudinal and transverse dimensions of the film cassette.