in 1981 canon introduced a self-contained autofocus lens, the 35–70 mm af, which contained an optical triangulation system that would focus the lens on the subject in the exact center when a button on the side of the lens was pushed. it would work on any canon fd camera body. nikon's f3af was a highly specialized autofocus camera. it was a variant of the nikon f3 that worked with the full range of nikon manual focus lenses, but also featured two dedicated af lenses (an 80 mm and a 200 mm) that coupled with a special af viewfinder. f3af lenses were only supported by the f3af, the f501, and the f4. nikon's later af cameras and lenses used an entirely different design.