Reassembly of lens mount on Canon FDn 400mm F1:4.5 telephoto

Barton-Wood · Joined: 14 Aug 2015 Posts: 2

Hi everyone. I am a newcomer to the forum.

My background is that of a multi-disciplined engineer having served an apprenticeship as an optical instrument maker at Rank Kershaws in Leeds during the early sixties and also worked at Rank Taylor Hobson in Leicester during the seventies before branching out into other areas including electronics systems design and teaching in both FE and HE.

As for hobbies I like making all sorts of technical devices, enjoy cycling and walking and spend a lot of quality time with my grand-kids. I have a number of longer, ex-government lenses from 36" F1:4 down to 12" F1:4 that I am modifying for use with my digital camera by fitting them with focussing mechanisms derived from legacy/scrap 35mm MF prime telephoto lenses.

I have just purchased a Canon FDn (New FD Mount type circa 1981-on) 400mm F1:4.5 telephoto lens for use on my Samsung NX300 CSC with a view to using it as a lightweight long lens for wildlife photography - it is one of the lightest 400mm lenses of that aperture and also has good performance from wide open to F1:11 and stops down to F1:32. However, from F1:16 down it softens noticeably from the effects of diffraction.

Unfortunately, the lens had a problem in that the mount was falling off so, optimist that I am, I partially dismantled the mount in order to reach the offending screws and to tighten them. This was successfully carried out BUT I have not been able to reassemble the mount/iris linkage assembly back into the lens such that it functions and am at a loss as to how I can do this despite spending some time studying the mechanism. I was confident that this would be well within my capabilities but I appear to have been somewhat over optimistic. There is obviously a technique to it but without any lens data I am beginning to think that I must seek help.

I should, therefore, like to ask if anyone in this forum knows of a technique for solving this particular puzzle: has a service manual that explains the procedure or know of someone who could carry out this "Simple Task"? I should like to have the thing reassembled before the end of summer so I can take my grandkids out on at least one wildlife-spotting field trip during the summer vacation and to test this addition to my collection.

Yours hopefully,

John

Attila · Expire: 2025-11-18

Nice to see you John!
Fingers are crossed, pretty uncommon lens Sad

cooltouch · Joined: 15 Jan 2009 Posts: 9097 Location: Houston, Texas

Hi John,

Welcome to the forum. It's nice to have someone with your level of optical experience here.

I used to own the nFD 400/4.5 and I loved it -- until it was stolen. Crying or Very sad

My copy had some very light fungus in the IF assembly, but I never tried opening it up because I knew that if I futzed with that IF assembly I'd never get it back together properly. So I have no direct experience to offer. About the only thing that comes immediately to mind is the mount itself. The nFD mount is quite complex and rotates about within itself. Might it need to be rotated in order to get things to link back up properly? Or have you already tried this?

I did encounter a similar problem with a Vivitar Series 1 28-105, though. It had a very long lever arm that reached down and coupled with the iris assembly that was very difficult to finagle loose and just as difficult to get reattached. Just a whole lot of repeaded attempts until I finally got it where it needed to be.

I take it your in the UK? Here on this side of the pond, the acknowledged expert on FD lens and camera repairs is Ken Oikawa. His phone is (951) 246-9136 and his address is:

28288 Worcester Rd.
Sun City CA 92586

Just in case you get desperate enough to send it off, that is.

In any case, best of luck, and I hope to see more posts from you in the future.

Barton-Wood · Joined: 14 Aug 2015 Posts: 2

Hi,

thanks for the welcome and for the information regarding Ken Oikawa but would ask if you are able to send me his email address or a link to his website if he has one?

Again, many thanks and best wishes,

John.

cooltouch · Joined: 15 Jan 2009 Posts: 9097 Location: Houston, Texas

Ken's really old school. No email address, no website. The telephone's about as high-tech as he gets.