AT-1 "Old FD" or "New FD" Mount : LUSENET : Canon FD : One Thread


I'm a little confused on the type of FD lens mounting system my AT-1 uses. It has a Breech Lock twisting ring mount that I beleive is known as the "old FD" mounting system. Is this correct?

Am I limited to using only "old FD" mount lenses on my AT-1 or will the "new FD" mounts fit?

When I look at FD lenses on Ebay, most don't indicate either an "old FD" or "new FD" mounting. Is it safe to presumed them to be "new FD" unless it says otherwise?

Thanks in advance for your help.


-- Jack O'Neill (, September 29, 1999


The silver ring is the "breech lock" or "old FD" system. The "new FD" or "bayonet" was introduced in the very late 70's and is a redesign to make the lenses easier to mount on the body. Since the actual camera mount did not change the old and new mounts are compatible and interchangeable. The new FD lenses are generally all black (no silver ring) except for some long lenses.

The FD mount was introduced in the early 70's and was an evolution of the FL mount. You can use FL lenses on later bodies (& vice versa) but you will have to use stop down metering. Very much like Nikon's F mount/AI mount progression. While the FL's are useable don't confuse them with FD's.

Some lenses are available only in the new FD mount, primarily the later zooms while others are available in both mounts. The older lenses are generally considered stronger and more robust. The new lenses are often lighter, a few were new optical designs and have improved coatings.

See these sites for more info: and and


-- (, September 30, 1999.

Also the "new" FD mount is not a true bayonet mount. Like the breech lock system, the lens mounting surface and the camera mounting surface do not move against each other during the mounting/dismounting action. So there is no more wear on the mount with the new mount versus the old mount.

Also ALL newFD lenses are of the "bayonet" mount (all black). Also all the newFD lenses are multi-coated (SSC). The old mount lenses came in single coated (SC) and multi coated (SSC) versions.

-- Terry Carraway (, October 01, 1999.

Oops, not ALL newFD lenses are "bayonet" mount, the 35mm Tilt and shift Lenses is breech lock in old or new FD.

-- Terry Carraway (, October 05, 1999.

I have both old and new FD lenses and there is really not much difference in them. The newer style was to compete with the bayonet mounts of the other makers. The older style is actually a stronger and more reliable mount. Lens changing is a snap with either.

-- Tom Williams (, October 16, 1999.

I have an FD extender 2X-B. From descripions above, this fits into the "old type" category (silver ring). However, I thought this "B" type extender was a later innovation (approx '82). Any clues as to when the 2X-B came onto the scene.

-- Garnet (, October 16, 1999.


All the extension devices seem to have been made with the breech mount (silver ring) no matter when they were made. This includes the 2x A and B converters and the FD macro extensions tubes 50mm, 25mm, and 15mm.

As to one mount be stronger than the other, this is not so, they are the same mount. In the new FD the ring is integrated into the lens body which turns to mount. The only real difference is the breech mount type uses friction to lock the ring from turning, while the "bayonet" mount uses the lock button.

Some people feel that the breech mount can adjust to wear, but the basic FD mount design is such that there is no movement between the mounting surfaces during the mounting process. The two surfaces mate and stay in the same position during the mounting.

-- Terry Carraway (, October 25, 1999.

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