Shutter arrangement for a motion picture camera

Claim 1

In a motion picture camera, the combination comprising: a film aperture; a blade serving as a shutter for the film aperture, the blade being rotatable so as to define open shutter and closed shutter positions; a controllable drive mechanism for the blade; a controllable stop mechanism for the blade; circuit means for generating an oscillating signal the frequency of which defines the camera frame rate, the circuit means being operable in either a first mode of operation in which the frame rate is substantially constant or a second mode of operation in which the frame rate varies to provide shutter speed control of exposure, the oscillating signal defining first and second subintervals during each period of oscillation; a diaphragm; a servomechanism for adjusting the aperture size of the diaphragm when the circuit means operates in its first mode of operation so as to provide aperture size control of exposure when the frame rate is substantially constant; mechanism controlling means responsive to the oscillating signal for controlling the drive mechanism and the stop mechanism so that during the first sub-interval the stop mechanism releases the blade and thereafter the drive mechanism provides torque to rotate the blade, and during the second sub-interval the blade coasts until its rotation is arrested by the stop mechanism, the stop mechanism so arresting the rotation of the blade at an open shutter position; the circuit means including a controllable switch, first and second timing networks selected by the controllable switch for timing the duration of the second sub-interval in the first and second modes respectively, the second timing network including a photoconductor for adjusting the timing of the second timing network in accordance with object light so as to provide an adjustable exposure time; detecting circuit means connected to the servomechanism for providing an indication of whether the servomechanism has adjusted the diaphragm to maximum aperture size; and means responsive to the provided indication for automatically controlling the controllable switch.