Abstract: A camera with a focusable objective including an axially shiftable lens member has two ancillary projection systems continuously or intermittently intercepting incident light rays downstream of that lens member and deflecting them onto respective inputs of a photoelectric comparator which emits a coincidence signal whenever these light rays project substantially identical images of an object to be photographed or filmed. One of the projection systems may include a periodically movable element which varies the relative orientation of the two beams constituted by the deflected light rays so that different angles of incidence give rise to a coincidence signal in different parts of a sweep cycle; in one position of this element, in which the incident rays will have a predetermined orientation (e.g. parallel to the objective axis) with proper focusing, a position sensor generates a correlation signal.

Abstract: A method and apparatus for the resynchronization of the transport of movie film (image carrier) with the movement of another information-carrying medium such as sound tape film. Speed control and synchronization signals are produced by means of sensing the sound tape movement which provides control synchronization signal, monitoring the image frames for each sequence on the movie film by means of a counter, and comparing in a coincidence circuit the image frame count signal with the signal from the sound tape. Desynchronization of the movie film and tape is indicated by the absence of a predetermined relationship between the number of image frames in a given sequence and the signal from the sound tape, whereupon the coincidence circuit energizes an appropriate control means via a switching mechanism, such as a gate circuit, which produces a resynchronization of the film and the sound tape.