Open-loop stepper motor controlled shutter

An exposure control system for a camera having a scanning type shutter mechanism for forming a range of aperture areas through which a photographic image is formed includes a stepper motor and a regulator or open loop control system therefor, to actuate the shutter mechanism between its open and closed positions in correspondence with a predetermined set of aperture area defining curves selected in accordance with sensed scene brightness and subject reflectivity levels. The stepper motor is operated at a relatively low rate of speed in order to avoid shutter blade mechanism overshoot and to achieve substantially the same shutter mechanism positioning accuracy as that achieved with a closed loop control system. Employing a stepper motor together with an open loop control system for scanning shutter mechanism actuation in the above member, results in a simplified exposure control system that is both compact and relatively inexpensive.