the soft-focus effect, a wide range of results are possible. The lens may also be used as a standard short telephoto. It offers all FD features. The Reflex 500mm 8 lens is a supertelephoto mirror lens of high optical quality which shares the unique characteristics of all mirror lenses with a central obstruction. Since its aperture is fixed at 8, it lacks FD signals and controls. It must be used in manual or stopped-down metering mode. Two other specialty lenses are the fisheyes. Two versions were produced. The 7.5mm 5.6 is a circular fisheye, rendering a 180 degree field of view in a 23mm image circle. It requires manual operation and stopped-down metering. The 15mm 2.8 is a full-frame fisheye, rendering a 180 degree field of view across the diagonal of the 35mm frame with the considerable barrel distortion of a fisheye lens. It includes all FD features and may be used with automatic exposure. Both lenses include internal filters. The remaining specialty lenses are the 20mm 3.5 and 35mm 2.8 Macrophoto lenses. Similar to microscope objectives, they provide magnifications of 4X-10X and 2X-6X respectively when mounted on the FD Auto Bellows. They can only be used with a bellows, via an FD adapter; while the adapter can mechanically mount them directly to a camera, they cannot function optically. They are not properly FD lenses, but are listed here because they are part of the whole system. FD autofocusing lenses Before the FD mount was obsoleted by the EOS system, Canon built four autofocus lenses. Of these, only the FD 35-70mm f/4 AF was capable of autofocus on all FD cameras. The others, known as AC lenses, offered autofocus only on the T80 camera. The FD 35-70mm f/4 AF contained an entirely independent autofocus system and was among the world's first autofocus zoom lenses (the Pentax ME F was the first ). The autofocus system was activated by a button on the side of the lens, and involved no communication with the camera body. It was reasonably accurate with still subjects, but was too slow to be a practical solution for moving subjects such as sports. Further development produced the AC derivative of the FD mount. Three AC lenses were manufactured, the AC 50mm 1.8, AC 35-70mm 3.5-4.5, and AC 75-200mm 4.5. All were released in April, 1985 alongside the Canon T80 camera, which was the only camera ever manufactured