Abstract: A variable aperture shutter is provided with a pair of shutter blades reciprocably mounted on a drive formed by an endless belt stretched between, and driven by, a pair of capstans. One blade is attached to each side of the endless belt loop and both extend across the width of the loop. Reversible rotation of the capstans controls the separation of the blades. A light beam, aligned orthogonally with the shutter, is intercepted when the shutter blades are in the closed position, with their adjoining edges abutting. Light is permitted to pass through a gap between confronting blade edges upon controlled rotation of the capstan drive. Apertures of varied sizes and shapes may be generated by superimposing two or more shutters and selectively controlling their capstan drives.