Canon FD 50mm/f1.4 S.S.C. - Aperture Stuck ? : LUSENET : Canon FD : One Thread

I recently acquired a very clean FD 50mm/f1.4 S.S.C. lens. It was manufactured in 1975 and spent its life (until now) on an old F-1. I purchased it to replace the FDn 50mm/f1.8 lens that came with my A-1. Since this is my first breech mount lens, I am unsure as to how to check to see that the aperature is functioning properly.

I understand that the FDn lenses when unmounted open to f5.6(?) so I can see the aperture blades when looking through the lens, which is the case on my FDn 50mm/f1.8. I also understand that the old breech mount lenses are wide open when unmounted so one cannot visually inspect the aperture blades.

My question is this - How can I see/test/inspect the aperture on the 50mm/f1.4 S.S.C. or ensure that it is functioning properly ? (or at least know whether it stuck or not)

Thanks in advance to any and all who reply.

-- Jeff Lloyd (, January 17, 2000


To manually stop down a breech lock lens hold the lens with the camera end towards you and the dot on the ring at the top. With a small tool (screwdriver, toothpick etc.) press down on a small leaf spring half behind the mounting ring near the dot. The mounting ring should release and turn counter clockwise about 1/6 of a turn. Move the stopdown lever (the one near the 4 oclock pos'n) counter clockwise until it locks. At this point you should be able to vary the diaphragm opening with the aperture ring.

If you set the aperture ring to the smallest setting and flick the stop down lever you can see if the lens is stopping down or is sluggish. Often there will be oil on the diaphragm blades that cause them to stick. You can also try this on the camera by setting the minimum aperture, a shutter speed of 1/60 and looking thru the lens with the back open or off. You should see the smallest aperture the lens is capable of. If it's larger, then the lens is sluggish.

When you're done, move the stop down lever clockwise so it's free to move and turn the mounting ring clockwise back to the latched position.

-- Duane K (, January 17, 2000.

Canon FD lenses are the most difficult to inspect because you can't operate the diaphragm by merely flicking the actuating lever, as with other lenses (Minolta, Pentax, Olympus, etc.).

A simple trick is to bring your camera body along or borrow one from the store where you're inspecting the lens. If the body has a stop-down lever, use it to operate the diaphragm. With the camera back open and shutter set to "bulb" you can inspect the front and rear of the diaphragm.

A little oil may not necessarily cause sluggish diaphragm operation. To check, set the shutter speed to 1 second or 1/2 second and cycle the lens through every f/stop. Do this several times while observing how crisply the diaphragm opens and closes.

Sometimes even a slightly sluggish diaphragm can be pepped up by operating it several times before a shooting session. Or if your camera body has a stop-down lever and permits stop-down metering, use the lens that way - assuming it's a favorite lens and worth the trouble.

-- Lex Jenkins (, June 10, 2000.

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