Special-purpose Lenses
Canon offered six specialty lenses for the FD mount. The TS 35mm f/2.8 lens is a perspective control lens. It may be tilted ±8 degrees for depth of field control, or shifted 11mm for perspective control. Though it uses the breech-lock mount, it is not literally an FD lens since its diaphragm is operated manually and must be used with stop-down metering.
The 85mm f/2.8 Soft Focus lens is designed for portraiture. The photographer may introduce three levels of spherical aberration via a push-pull ring. Since aperture also affects the magnitude of 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.
Two other specialty lenses are the fisheyes. Two versions were produced. The 7.5mm f/5.6 is a circular fisheye, rendering a 180 degree field of view in a 23mm image circle. It requires manual operation. The 15mm f/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 f/3.5 and 35mm f/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.
Read more about this topic: Canon FD Lens Mount
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