The equipment incorporates a film cassette holder (44) and a holder for prim. stops provided between the X-ray source and object to limit the radiation beam. Different sizes of cassette (45) can be accommodated with the provision of a system which senses the position and format of the cassette. Rods or sleeves (59,60) are equipped at one end with angle-sensing potentiometers (61,62) and at the other end with touch levers (63,64). The signals from the potentiometers may be used to rotate the appropriate size of prim. stop automatically into the path of the X-ray beam.
