The Canon FD 135 mm f/2.5 lens was one of the first of its kind, utilizing the manufacturer's new FD mount. It features the old FD style locking ring to secure this prime manual focus lens to a camera, and consists of six metal lens elements, weighing in at 22 ounces. The lens has a minimum focus distance of 5 feet and minimum aperture of f/22, with enhanced image delineation at the full aperture opening to help minimize field curvature. The lens uses 58 mm filters, caps, and accessories, and was designed to be compact enough for a variety of photographers.