Abstract: A mechanism which can be utilized to drive a rotating sector disc type light shutter with a high degree of precision, so as to control light exposures that are made through a stationary aperture. Unlike the prior art, this inventive mechanism can be used to extend the exposure duration range almost indefinitely. In essence, this is accomplished with the inventive mechanism by stopping the motion of the sector disc shutter, with the open portion of the sector disc aligned with the stationary aperture, and then, after a preset elapsed interval, restarting the disc to close the aperture and terminate the exposure. Also unlike the prior art, this inventive mechanism obviates the need for critical timing.