Problem with Canon FD lenses

I have been returning to and expanding my old film based Canon kit (all FD, never saw the point of AF) but I've hit a snag, a couple of my

telephotos won't stop down. At all. They are just stuck at full aperture. I'm not so bothered about the 100mm f2.8, but I'd hate to be without

my 135mm f2

 

Does anyone know if there is a quick fix for this?

A stuck aperture is usually an indication that grease has migrated to the diaphragm blades, a result of being stored in a warm or hot location. The only reliable solution is to have the lens disassembled and cleaned.

 

On the other hand, a stuck diaphragm might be due to lack of use. A used FD 50mm f/1.4 SSC lens I bought several years ago had a stuck diaphragm which I assumed to be due to oily blades. However, after working the aperture lever for a few minutes, the diaphragm began to work properly. There was no evidence of oil on the blades. The coil spring in the aperture mechanism may be binding due to long term storage.

Gordon, I'm wondering whether a small amount of oil on the aperture blades is problematic. I have had a lens with so much oil on the blades that its aperture stuck open, and obviously I had to get it serviced. But I have two other lenses with a small amount of oil on their blades, and they seem to work fine. Any thoughts?

I have some lenses that work fine with a little oil on the blades. It's a matter of degree. At some point, the amount of oil may increase and/or the existing oil may begin to congeal and attract dust. Eventually, the blades will not be able to close to the set aperture quickly enough, resulting in overexposure. You could check your lens periodically by cycling the shutter while looking through the back of the camera to see if the lens is closing down to the correct aperture.

They are failing to stop down in on an F-1n/T90/AE-1, one is a 'new' one from ebay and the other (the 135 f/2) is one of my

own, which I have used in the past without difficulty...

 

I guess it's buy a new one for the 100mm and try to find a repairer for the 135mm.

 

Any suggestions (for the UK) ?

Hi Barry

 

I had an FD lens serviced by a chap in Clay Cross. He was very reasonable and knew his stuff. Just Google Camerarepairer and you should get his web site.

Barry,

 

I bought a Canon bayonet mount 100 f2.8 on ebay knowing the aperture was oily and stuck. I have read this lens if

known for oil on the aperture. I got it cheap and I wanted to try my hand at it. I had good luck but found everything

that should not be taken apart only after I took it apart. Have you ever seen seen 300 steel micro balls fall out of a

lens?? I didn't have to disassemble that part and it was not easy to get it back together mostly because I couldn't

see them very good. I needed magnifiers. Cleaned (dunked) the aperture assembly with lighter fluid. After

reassembly, calibration of the aperture and setting infinity focus, it works fine, looks like new, with sharp photos and

proper exposure. My job is technical so the dissassembly did not bother me and I only had $10 to loose anyway.

You may want to consider giving it a go. I can tell you what NOT to do.

Tim,

LOL, I took apart a 70-200 once for the same reason, and lost quite a few steel balls :)

Since more than one of your lenses are behaving this way it may not be oil on the aperture blades. They wouldn't all bind up at once.

 

Instead, I suspect the DOF preview lever is in the "illegal" position when you mount the lens. If you activate the DOF preview and then mount a lens you will not be able to change the aperture. To remedy the situation, remove the lens, return the DOF preview lever to the normal position and then re-mount the lens.

 

I hope that helps.

 

Jim C.