A film winding and focal plane shutter cocking mechanism includes a safety gear that has an annular rib secured to one face. A cut out in the rib is engaged by an end of a lever which is moved by a sliding bar when the shutter actuating button is depressed. An interlocking mechanism which is operated by the safety gear prevents movement of the sliding bar again until the film winding and shutter cocking mechanism has been manually actuated to prevent double exposure.