an earlier cinematographic technique or wipe effect, in the form of an expanding or diminishing circle, in which a part of the screen is blacked out so that only a portion of the image can be seen by the viewer; usually the lens aperture is circular or oval shaped and is often expanded or contracted as the film rolls, often from one scene to the next; known also asdiaphragm. The camera movment is often termed iris wipe,circle-in/circle-out, or iris-in/iris-out; also refers to the adjustable opening in the lens that allows light to pass through - the measurement for the iris opening is f-stop