The Canon FD 55mm ƒ/1.2 AL is a camera lens made by Canon, first introduced alongside the Canon F-1 single-lens reflex camera in March 1971. It was the first lens for any 35mm SLR system to incorporate an aspherical element.[1] The lens was manufactured until 1980.
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Maker | Canon |
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Technical data | |
Focal length | 55 mm |
Aperture (max/min) | ƒ/1.2 – ƒ/16 |
Close focus distance | 0.6 m (24 in) |
Max. magnification | 0.11 |
Diaphragm blades | 8 |
Bauwesen | 8 elements in 6 groups |
Physical | |
Max. length | 55 mm (2.2 in) |
Diameter | 75.8 mm (2.98 in) |
Weight | 605 g (21.3 oz) |
Filter diameter | 58 mm |
History | |
Einführung | March 1971 |
Discontinuation | 1980 |
Design
editThe FD 55mm ƒ/1.2 AL uses a variation of the double-Gauss lens design, in which the positive meniscus element of the front Gauss pair is aspherical. In total, the lens has 8 elements in six groups: a front element, two Gauss pairs, and three additional rear elements.
Variants
editIn March 1975, Canon introduced a version of the lens, known as the FD 55mm ƒ/1.2 S.S.C. Aspherical.[2] Although, this version was the first to formally signify that it is multicoated, the original version without S.S.C. engraving has used this type of multicoating as well.[3]
Radioactivity
editLike a number of other contemporary lenses, the Canon FD 55mm ƒ/1.2 AL incorporated thoriated glass,[4] a kind of optical glass that is doped with thorium dioxide. The inclusion of this compound makes the glass radioactive.
Over time, thorium decay causes F-centers to form in the glass, resulting in an amber discoloration. The discoloration can be repaired by exposure to a source of ultraviolet radiation, such as direct sunlight.[5]
References
edit- ^ "FD55mm f/1.2 AL – Canon Camera Museum". Retrieved 2019-01-17.
- ^ "FD55mm f/1.2 S.S.C. Aspherical – Canon Camera Museum". Retrieved 2019-01-17.
- ^ "Canon inerchangeable lenses FD instructions – www.flynngraphics.ca" (PDF). Retrieved 2023-06-15.
- ^ "Radioactive Lens – Canon FD 55mm f/1.2 S.S.C. Aspherical". YouTube. 2011-01-10. Retrieved 2019-01-17.
- ^ "Radiation-induced Discoloration" (PDF). www.sealandair.fr. BIRNS, Inc.