Canon FDn lenses WTF?

[Uglee]

Anyone with a FD (newer) 50mm 1.4 and 1.8 lens, have you noticed if your lenses aperture diaphragm prematurely closes to its minimum aperture in stop down mode prior to it actual setting? For example, my 1.4 will reach its smallest aperture at f8.5 and my 1.8 will be at its smallest one click before f11, both have a minimum of f22. The aperture blades will open and close freely to its minimum and max when not mounted on a camera. This only occurs when mounted. My older breach lock lenses do not do this.

I have have taken apart and reassembled the 1.4 a couple of times making sure the aperture diaphragm is clean and moving freely and is set in the lens properly. Everything works as it should until I mount it on a body. I have tried the lenses on various camera bodies, F1, A-1 and EF with no change.

So has anyone else notice this or do I have two lenses in need of an attitude adjustment?

 

[rbiemer]

I own and use both of those lenses on an AE-1p and (more often) on my T90.
Neither of mine do that.
Rob

 

[raid]

The lenses may need some adjustments in the aperture mechanism.

 

[cmc850]

you may want to verify the actuating lever for the aperture pin in your camera body is not in some way bent or not fully depressing the lenses levers.

In my experience, the behavior of the diaphragm on FDn lenses when off the camera is erratic - mine essential leave the f-stop at an opening someplace in the middle when not mounted - but all settings produce a unique and predictable opening when mounted.

 

[Uglee]

Thanks for the replies. With the diaphragm removed from the lens the aperture moves freely. With the lens base lock turned to allow manual manipulation of the apture lever, it also moves freely from minimum to max. The actuation levers on the three camera bodies give consistent results with the two lenses, however my older breach lock lenses work perfectly on these same cameras. I believe there may be something amiss in the lens base and may not be mounting correctly when locked in place on the camera.

 

[cmc850]

Makes sense - did not realize you had tried several bodies. I do know that when mounting my FDn lenses on a cheap EOS-M adapter, I have to make certain I push the lens and mount together firmly before rotating, and for some reason, also need to set the diaphragm preview lever on that rig to the lock position upon initial mount for the aperture to function fully.

The breech lock system always had a strength and play reduction advantage over common bayonet lenses, but it seems the inconvenience in use prompted Canon to come up with the FDn bayonet variation, imperfect as it seems now.

 

[Uglee]

I found the problem. It was a deformed actuation lever in the base. I was able to carefully bend it back just enough to work properly. I am happily surprised at how serviceable this lens is.