Canon FDn 35mm f/2 inf-focus stops aperture reaction

Terkild · Joined: 22 Jul 2014 Posts: 8

Hi,

I have just bought a used Canon FDn 35mm f/2 and am beginning to think i made a bad decision, as the lens is acting kind of weird (was so looking forward to playing around with it, so i am a bit disappointed). So i really hope you can give me some advice on what to do.

At first sight, the glass is in great condition and focus/aperture runs smoothly. However, when i started using it i noticed that going the last range of the focus ring (from 8ft to infinity) it go really tough. So i thought the focus-ring was somehow badly lubed or something. But then i noticed that there seem to be some interplay between the focus-ring and the aperture on this lens:

When the aperture is at f/11-22 and i turn focus to infinity i cannot stop aperture down below f/11.

If aperture is f/2-8 and i turn focus to infinity (still tough the last way) the aperture ring turns nicely, but the blades/diaphragm does not react.

I also noticed that despite turning the aperture from f/11 to f/22 the diaphragm opening stay the same (and the "lever" on the back of the lens stop moving after f/11).

I am by no means a lens expert, but shouldn't the focus and aperture rings be pretty independent? Can anyone give good suggestions for what might be wrong and if possible, how i fix it?

Really hope you can help! Thank you in advance!

/Terkild

Gardener · Joined: 22 Sep 2013 Posts: 950 Location: USA

Chances are that someone took the mount off, and did not put it back together correctly. Take a look at the mount, specifically at the three little black screws on its side that hold it in place. Does it look like they had been removed at some point?

Terkild · Joined: 22 Jul 2014 Posts: 8

Gardener · Joined: 22 Sep 2013 Posts: 950 Location: USA

It's not really difficult, but sort of hard to describe. The key is to put it back together in activated state. Do you know how to push two little pins in the mount and turn it to check the aperture action off camera. That is the position it should be when it's assembled. Other than that it's a matter of aligning levers.
I mean I am not 100% sure its the mount but it would be the easiest solution - I have not ever taken apart 35/2 completely, but I've been inside 24 and 28 - and they are not simple design, not by any stretch of imagination.

Terkild · Joined: 22 Jul 2014 Posts: 8

How would you approach the dis- and assembly of the mount. The only guide to FDn i can find uses an approach from the front unscrewing the nameplate and then the elements. But there are also the 3 black screws around the mount "ring" that hold it in place. If you're right that it is the mount that is wrongly assembled, which way should i approach, and should i have the mount in the activated state at both dis- and assembly or?

Thanks again for your help!