Abstract: The disclosure relates to photographic cameras adapted to receive film cartridge assemblies enclosing rotatable film disk units. When a film cartridge assembly is received in the camera, it cooperates with a camera mechanism that opens an exposure window in the cartridge assembly and rotates the film disk unit incrementally to locate successive exposure areas accurately in exposure position. Various novel camera mechanisms are also disclosed for supporting the film exposure area in a predetermined film exposure plane and for preventing accidental exposure of the film to ambient light.