Abstract: In a device for recognizing the format of a film cassette for use in a film cassette holder, such as in an x-ray examination apparatus, a radiation receiver is disposed at a location at which radiation incident on the receiver is altered by a corner of the film cassette when the film cassette is inserted. The radiation receiver generates an output signal dependent on the radiation incident thereon, which is supplied to a processor which identifies the format of the film cassette whose corner caused the alteration in the incident radiation. Dependent on the format configuration, the alteration in the radiation may either be an occlusion of the radiation, or a signal indicating an absence of occlusion. The radiation may simply be ambient light, or may be radiation transmitted by a radiation transmitter allocated to the radiation receiver.