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Canon FD Lens Mount - 35mm Film SLR Camera Lens Mount

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The Canon FD lens mount was a manual focus lens mount used on Canon SLR cameras from 1971 until 1987.

The Canon FD lens mount was used by Canon on 35mm film SLR cameras from 1971 until 1987. The FD mount was based off of the earlier Canon FL lens mount. It was replaced by the Canon EF lens mount, which was designed for auto focus.

The Canon FD lens mount uses a breech lock system to mount to a camera. This is a less common method than the most used solution, the bayonet mount.

The Canon FD mount, introduced in 1971, offered several significant improvements and new features compared to its predecessor, the FL mount.

  1. Automatic Diaphragm Function: Unlike the FL mount, the FD mount supports an automatic diaphragm function. In the FL system, the user needed to manually stop down the aperture of the lens to the desired f-stop before taking a picture. With the introduction of the FD mount, this was no longer necessary. The FD mount allowed for automatic control of the aperture, meaning the aperture would automatically close down to the selected setting when the picture was taken and then open up again to the maximum aperture. This made operation quicker and easier, especially in rapidly changing light conditions.

  2. Full-Aperture Metering: The FD mount introduced full-aperture metering, an advancement over the FL’s stop-down metering. This meant that light metering could be done with the aperture wide open, providing a brighter viewfinder image and allowing for more accurate focusing and composition. When the picture was taken, the camera would automatically stop down the aperture to the selected setting, then open it back up again.

  3. Automatic Exposure Control: The FD mount included a mechanical linkage that allowed the camera to control the lens diaphragm. This enabled automatic exposure control, where the camera could select the appropriate aperture based on the metered light. This feature made it easier for users to get correct exposures, especially in challenging lighting conditions.

  4. Mounting Mechanism: Both FL and early FD lenses used a breech-lock mount. However, later versions of the FD mount (known as the “New FD” or “FDn” series) switched to a bayonet-style twist-lock mount, which was faster and easier to use.

The lens mount on a Canon FD 50mm f/1.8
The lens mount on a Canon FD 50mm f/1.8

I’m not a fan of the breech lock system. The design makes it difficult to clean dust and debris that gets into the breech lock.

The later “new FD” lenses made mounting and len removal easier. Earlier versions could be mounted incorrectly, causing lenses to get stuck.

Over tightening or changes in temperature can cause lenses to be difficult to remove.

The highest quality FD lenses the Canon produced were ‘L’ series lenses. These lenses contained optical technologies that were more expensive to produce. This included aspherical optics and fluorite lens elements.

These lenses can be visually identified by the red rings around the front of the lens. This design choice was used on EF lenses and continues to be used on current RF mount lenses.

Three of the autofocusing FD lenses will only work with the Canon T80. The lenses can be identified by their AC designation.

The FD 35-70mm f/4 AF, is the only FD lens that will autofocus on all camera bodies.

This list of what camera use Canon FD lenses goes into more detail about the specific models listed below.

Canon produced a full linenup of camera lenses. This includeds, tilt-shift, soft focus, reflex, fisheyes, macro, and bellows adapters.

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The only OEM option is the Canon TS 35mm f2.8 S.S.C lens. At the time of writing, copies can be found on eBay for $500 or more.

One of the reasons the lenses are so expesnive is that they can be adapted onto mirrorless camera bodies. The manual controls are easy to use with liveview.

Flange Distance & Mount Diameter

Canon FD 28mm f/3.5 Lens
Canon FD 28mm f/3.5 Lens
Lens Mount Flange Focal Distance Mount Diameter
Canon FL 42.00 mm 48.00 mm
Canon FD 42.00 mm 48.00 mm
Canon EOS (EF) 44.00 mm 54.00 mm
Canon RF 20.00 mm 54.00 mm

The flange focal distance determines how the lens and camera interact to form an image on the camera’s sensor or film plane. An FD lens has been designed to mount 42mm away from the image sensor or film plane.

If the flange distance is not correct, the lens may not be able to focus across its entire range. If the lens is farther away, it will lose the ability to focus to infinity. If the lens is too close, it will not be able to focus on close subjects.

The mount diameter also increased over time. Both the FL and FD mounts have a diameter of 48mm, but the EOS (EF) and RF mounts increased this to 54mm. A larger diameter can allow for larger lens elements and wider apertures, which can improve image quality and low-light performance. It also provides more room for electrical contacts, allowing the camera and lens to communicate more information for functions like autofocus and image stabilization.

When it comes to adapting lenses to different camera systems, the flange focal distance is the determining factor. If you have a lens system with a shorter flange distance (like the Canon FD mount) and you want to adapt it to a camera system with a longer flange distance (like the Nikon F-mount or Canon EOS EF), you’ll encounter focus problems.

Canon’s RF mount, designed for mirrorless cameras, has a 20mm flange distance. A shorter distance is possible because there is no mirror taking up space in the camera.

35mm camera without a lens mounted
EF Mount on a Canon EOS 650
Updated on 2023-02-06
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