The Canon FD lens mount is a physical standard for connecting a photographic lens to a single-lens reflex camera body. The standard was developed by Canon of Japan and was introduced in March 1971 with the Canon F-1 camera. It was the primary Canon SLR lens mounting system until 1987 when the cameras from the Canon EOS series were first produced using the new EF lens mount. The last camera in the FD system was the Canon T60, from 1990. The FD mount replaced Canon's earlier FL mount (which in turn had replaced the R mount); FD-mount cameras could use FL lenses in stop-down metering mode. There is no known meaning for 'FD', and Canon has never disclosed what, if anything, it stands for.
Although the Canon FD system enjoyed huge popularity in the 1970s and 1980s, the mount system--with no provision for auto-focus--is now obsolete, and Canon FD cameras and lenses are available for low prices on the second-hand market. This makes the system very attractive to 35mm film photographers who demand the highest optical quality,[1][2] but who do not need auto focus capability.
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The FD lens mount is a breech-lock mount. The advantage of this type of mount is that the contact surfaces between the body and lens do not rotate against each other when the lens is mounted. This prevents any abrasion, which could conceivably reduce the very precise lens-to-film distance. The disadvantages include slower lens changes; later FD ('New FD') lenses mounted more like bayonet-mount lenses in that the photographer twisted the lens body to mount and unmount, even though the actual mount surfaces remained fixed.[3] Canon chose a bayonet-style mount for its new EOS system's EF lenses.
Like its FL predecessor, the FD mount system allowed automatic aperture function, but in addition, a new indexing pin supported full-aperture metering. Together with a signal pin for the "auto" setting of the aperture dial, this enabled integral auto-exposure. The first camera to utilize this was the Canon F-1, when equipped with the Servo EE Finder, in 1971. Later, the Canon EF from 1973 had automatic exposure built-in, as did the very popular Canon A-series cameras (save the AT-1) beginning in 1976. The FD mount has no support for the lens-body communication, electrical or mechanical, required for autofocus (the AC FD lenses, described below, are an exception), which was a primary reason for its retirement. While Canon could have adapted its mount to support auto-focus, as did other manufacturers, instead the company chose to make a clean break with the past and design a completely new interface with support for electrical signaling.
The earliest breech-lock Canon FD lenses (1971-1973) are recognizable by chrome (silver) bayonet-ring at the front (this ring is used to mount appropriate bayonet-type hood). In these 'chrome nose' lenses, Canon used two new proprietary lens coatings, designated "S.C" (Spectra Coating) and "S.S.C." (Super Spectra Coating). These were both multi-coatings, but indicated two quality grades. In the chrome nose series, only the large-aperture 55mm f/1.2, 50mm f/1.4 (regular and 'AL'-type) and 7.5mm Fish-Eye lenses used S.S.C. coating. On these lenses the breech ring can be rotated freely without mounting it on a camera body.
The second series of breechlock FD lenses (1973-1979) lenses is inscribed "S.C." in white or "S.S.C." in red on the front of the lens mount. S.S.C. coating was extended to most lenses in this series. The basic S.C. coating was, for the most part, limited to the more inexpensive lenses. According to Canon literature, the selection of S.C. or S.S.C. coating was made based on the lens's requirements for flare control, etc. This second series has two different ranges. In the earlier range the Auto-Exposure remained a green "o" as did the chrome nose lenses. In addition, the breech ring could be rotated without mounting the lens on a camera. The later range used a green "A" to indicate that the lens was set for AE operation, and on these lenses the breech ring cannot be turned unless a small catch pin is pressed (mounting the lens on the camera does this). Additionally, pressing this range of lenses onto the camera causes the breech ring to rotate a few degrees, making it somewhat easier to mount the lens by having it partially secured as soon as it is pressed onto the camera body. There are exceptions to this rule, though, as for example the FD 300 mm f/5.6 S.C. has the later type of breech ring but still has a green "o" for the automatic aperture position. It has a built-in hood, though, so there's no bayonet mount in the front.
In 1978, with the introduction of the 'New FD' or 'FDn' series, the coating type was no longer specified on the lens front. All these lenses received S.S.C coating (with the exception of the 50mm f/1.8 lens).
A separate (and expensive) range of FD lenses was available for photographers who required the highest optical and mechanical performance. These used a variety of special technologies, including aspherical surfaces, fluorite optics, and low-dispersion glass. The earlier versions of these lenses are designated "AL", "Aspherical", or "Fluorite" on the front of the lens mount. The post-1979 'New FD' versions are designated "L" (said to indicate 'luxury' or 'asphericaL'). The "L" designation, and the famous red ring around the lens front, have continued in the current EOS autofocus lenses.
FD lenses were nearly all manual-focus lenses. In the mid-1980s, Canon did, however, manufacture four unusual autofocus lenses for the FD mount standard.
The first, the FD 35-70mm f/4 AF, contained a lens-integral autofocus system and was the world's first autofocus zoom lens. The autofocus system was triggered 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.[4]
Further development into autofocusing produced the AC derivative of the FD mount. Three AC lenses were manufactured, the AC 50mm f/1.8, AC 35-70mm f/3.5-4.5, and AC 75-200mm f/4.5. All were released in April 1985 alongside the Canon T80 camera, which was the only camera ever manufactured to take advantage of the AC lenses' AF capabilities. The lenses communicated with the T80 via electrical contacts and lacked an aperture ring, but were otherwise identical to the FD mount and could be used on those FD-mount cameras that could control the aperture, only without the AF capability. The AC lens-line proved to be a dead-end development, as Canon would abandon the capability in the two remaining FD-mount cameras it produced, the T90 and T60, and later introduce the EF lens mount.[5]
The 42mm flange focal distance of the FD mount is shorter than that of most other lens mounts. Although FD lenses can be mounted on most other types of camera with the appropriate adapter, the lenses cannot focus to infinity unless the adapter contains an optical correction element. FD lenses can however be mounted on Canon rangefinder cameras or other Leica screw mount cameras using the Canon lens mount adapter 'B', but rangefinder-coupled focusing is lost. FD lenses can also be mounted without optical correction on the Micro Four Thirds system, which has a flange focal distance of only 20mm. The 2x Crop factor of the Micro Four Thirds system means that the Field Of View is halved.
Following the introduction of the EOS camera line, Canon briefly marketed an adapter which enabled FD telephoto lenses to be used on EOS bodies. The adapter contained high-quality corrective optics and functioned as a mild tele-converter; it could not be used on normal and wide-angle lenses. The adapter was produced in limited numbers, with the intent of easing the initial cost of conversion for professional users with expensive FD telephoto lenses. These adapters are now scarce and highly valued, selling for around $1000 on the second-hand market. (The original 'new' price was $250). Other inexpensive aftermarket FD to EOS adapters are available and can be used at the cost of greatly reduced image quality, particularly at large apertures.[6]
Mechanically skilled photographers and technicians have successfully retrofitted FD lenses with alternative mounts, including the EOS mount.[7] Some Pentax users have had great success adapting FD lenses for use with Pentax "K"-mount cameras.[8]
It should also be noted that in 2011, FD to Sony NEX E video camera mounts are now appearing. This means that wide and ultra-wide FD lenses (especially their F2/F1.4) variants have become usable for video photography.
The original generation of FD lenses featured a silver locking ring at the base. Only that locking ring turns to lock the lens to the camera body; the lens body remains still.[9]
These lenses could only be used attached to a macro bellows; since they can't mount to a camera directly, they are not properly FD lenses, but are listed here because they are part of the whole system.[11]
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