Canon FD lens mount

When Canon FD bayonet it was the third generation of the R- bayonet, a lens mount for small format SLR cameras. It added the second generation, the FL -mount transmission elements added, which allowed TTL metering with full aperture and shutter priority and program AE. The FD mount was replaced around 1990 by the still current and incompatible with it an EF bayonet. Minor exceptions it seemed to only lenses with manual focus setting.

  • 2.1 period
  • 2.2 Design
  • 2.3 camera

FD bayonet

Period of time

The FD lens mount Canon front presented in March 1971. It was replaced by the EF mount, which was released in March 1987. The last camera the Canon T 60 released in 1990 for the system.


The FD lens mount adds to the FL lens mount an aperture simulator and three pins added, two immovable and movable:

Aperture Simulator

When aperture simulator it was a lever that was with a lens attached to the camera viewing direction left of the mirror. He allowed aperture metering and aperture, as well as automatic program.

For the aperture metering the simulator moved depends on the aperture set on the lens in a certain position, which transferred from a camera-side lever on the exposure meter. With this information, managed a measurement without stop down the lens

For aperture priority and programmed auto worked the transmission in the reverse direction. When pressing the shutter first moving a camera- sided lever aperture simulator to the desired position and then dazzled the lens to the preset value. The cameras A-1 and T-90 used the diaphragm mechanism for the automatic timer, while the aperture on the camera has been set.

Contact pin for the light intensity

The aperture metering needed the brightness of the lens, if necessary provided with a correction factor. This sent a contact pin with its length. He was in the bottom left of the camera viewing direction, ie between iris diaphragm lever and aperture simulator.

Automatic pin

For the aperture or the shutter Program AE rings of FD lenses had an additional position. In this the camera transferred the aperture using the aperture simulator to the lens. The camera received the information that the aperture ring was on automatic, communicated via a contact pin that slid into a hole of the camera's bayonet. This hole was located in the camera viewing direction right a little below the middle. On cameras which were not of this hole, the lens could not be recognized in automatic position. These were all cameras with Nachführbelichtung except for the F-1. In Automatic mode the preview button to control depth of field on the camera could not be pressed. AV-1 and AL-1 had a hole, but could not work in the automatic position of the lens.

Blank pin

The second fixed pin remained unused until the end of the FD system. He was reserved for future use and was in the camera viewing direction right of the mirror, so over the aperture simulator.

CAT autoflash

Some lenses had a nose near the filter thread, the mitdrehte with the distance scale. The nose is a special coupling ring flash (Flash Auto Ring ) to query the distance setting with potentiometer and transmit the flash unit electrically. The CAT system worked with the cameras F-1, FTb and EF in combination with the flash unit 133 D. The flash coupling ring was placed on the connection for the hood and had to be adjusted with a lever on the lens. The versions A2 and B2 came out later and were able to work together with macro lenses. CAT stands for Canon Automatic Tuning.

It was the lenses:

  • FD 35 mm, f / 2 (flash coupling ring A, A2, B and B2)
  • FD 35 mm, f / 3.5 (flash coupling ring A, A2, B and B2)
  • FD 50 mm f / 1.4 (Flash coupling ring B or B2)
  • FD 50 mm f / 1.8 (Flash coupling ring A or A2)
  • FD 50 mm f / 3,5 Macro (Flash coupling ring A2 or B2)


With the transition from chrome to black filter thread in the summer of 1973 modified the Canon bayonet a little. Could you date the union ring an unmounted lens move freely, so he was now engaged. On discontinuation of the lens to the camera, then the ring is turned by spring force something, so the lens could not fall off. In an engaged ring and the dimmer was locked in its home position. To manually move it, you had the ring on the lens cap in a little twist, so that it is just as flat nor did decrease.

The modifications included a lock button on the aperture ring for the automatic position.


For the FD system presented the following Canon cameras of the F-, A- and T- series before:

New FD

In June 1979, Canon introduced the modified bayonet New FD, but which offered no additional features, but only changed the handling. Now there was no union, but it had the whole lens as with other brands are rotated. To this end, the support surface with the transmission elements in the lens was mounted rotatably. There was also a rectangular release button on the lens, the einrastete after turning.

The previous FD lenses were often, but not officially distinguished with the addition of chrome ring. The tele-converter and intermediate rings kept in de previous solution, mostly as foreign lenses.

The New FD lenses were no longer working together with the CAT - flash system.

Autofocus lens

For the FD system, it was with the zoom FD 35-70 mm f / 4 AF already have an autofocus lens. His focus was working with its own battery and so that no additional transmission elements were required completely independent from the chassis. It was released in May 1981, found no greater dissemination.


With the extremely successful camera models AE-1 and A- 1, and so also with the FD- mount Canon rose to at the amateur cameras to the market leader.

AC bayonet (FD bayonet with autofocus transmission )

Period of time

Since there was already with the Minolta 7000 autofocus SLR, the EOS system but was still in development, Canon introduced with the AC bayonet a transitional solution that appeared in April 1985 and was discontinued the following year.


The AC bayonet completed the FD bayonet to 6 electrical contact pins on the lens, the mirror, so over the Blendensimulatur were in camera look to the right. As with late EF bayonet it was spring-mounted and gold-plated pins on the camera and also gold-plated contact surfaces on the lens. This electrical connection allowing the power supply and the control of an auto-focusing unit in the lens which was at the side of the lenses in the asymmetrically shaped housing. There were only three AC lenses:

  • AC 50 mm f/1.8
  • AC 35-70 mm f/3.5-4.5
  • AC 75 -200mm f/4.5

The AC lenses could also be connected to the cameras for the FD bayonet. Then, the focus had to be set manually. However, since the lenses had no aperture ring, they could be dimmed only by cameras with aperture and Program AE.


For the AC - lenses there was with the T-80, only a camera. She also works with the FD lenses.