Data is recorded on the film by the manufacturer prior to exposure at a first magnetic head azimuth angle. The camera magnetically records information on the film frame-by-frame at a second head azimuth angle with each exposure or shortly thereafter. Before exposure of any frame, the camera determines whether the frame has already been exposed by sensing the recorded signal amplitude at one of the two magnetic head azimuth angles. In order to prevent a double exposure, the camera transports the film past any frame having data magnetically recorded therein corresponding to the second azimuth angle.