Also Known As: Frames Per Second, FPS. Movies are created by taking a rapid sequence of pictures (frames) of action. By displaying these frames at the same rate at which they were recorded, the illusion of motion can be created. "Frame Rate" is the number of frames captured or projected per second. The human optical system is only capable of capturing about 20 images per second; hence to give a realistic illusion of motion a frame rate greater than this is required. Most modern motion pictures are filmed and displayed at 24 fps. Earlier films used lower frame rates, and hence when played back on modern equipment, fast motion occurs due to undercranking. See also: slow motion, fast motion, undercranking, overcranking, judder, motion artifact.