Abstract: A cassette including a light-tight housing having a pair of opposed sidewalls and an open end for insertion of a film into the space between the sidewalls. One of the sidewalls has an opening therethrough and the opening is surrounded by a first frame whose outer margin is covered by a panel opaque to visible light but transparent to X-rays. A second frame is disposed within the first frame and is provided with an illumination screen on its inner margin. The first and second frames have slots in the sides thereof for receiving pins on an actuator member which partially embraces the first frame, the slots in the second frame being inclined so that the illumination screen will move into and out of a position contiguous to the film in the space between the sidewalls when the actuator member moves back and forth longitudinally of the one sidewall relative to the first frame.