A dynamic iris is located on the imaging path of an optical lens system that includes a relay lens system and at least one projection lens system. A dynamic iris modulates image frames in an image data stream, resulting in a reduction in light transmission associated with the modulated image frames. A dynamic iris may be configured to change the size of its aperture as fast as or faster than the image frame period of the image data stream, and may be located at or near the pupil of a relay lens system, a projection lens system, or both. A second dynamic iris in the imaging path further modulates the image frames, resulting in a further reduction in light transmission. A dynamic iris may modulate an image frame based on an electronic preview of the image frame or based on metadata associated with the image frame.