How to fix a loose focus ring on a FDn 35mm f2

Discussion in 'Canon FD' started by hilbert5, Mar 24, 2007.

  1. Hi all,

    to be open I guess I have read here a kind of instruction quite some time ago
    but I cannot find it anymore. Maybe someone can provide the link or give me some
    advice.

    This is my problem:
    I own an FDn 35mm f2.0; the focus ring is a little loose. When focussing, I can
    juggle it about 2mm before the focus really changes. The juggling is only in the
    direction of its normal turning. This problem is not new and I did not care too
    much so far. But very often I have taken pictures in low light recently, and now
    this little juggling gets on my nerves when it comes to exact focussing.

    Hope someone of you specialists knows how to solve this problem.

    Cheers+Thanks,
    Ernst.
     
  2. awahlster

    awahlster Moderator

    Most likely the little screws that hold the barrel to the lens elements has come loose. You might try carefully pulling back on the rubber grip to see if there are screws underneath. If so line up the distance scale best you can and with a proper tiny screw driver tighten the screws keeping in mind they are tiny and to not over tighten them.
     
  3. Hi Mark,

    thanks for your quick answer!

    It there a trick to most "carefully pulling back" the rubber ring? (I am thinking something like warming it with a hair dryer):

    Cheers,
    Volker,
     
  4. Sorry. But Volker is one of my nick names in other forums.
    Read it as Ernst.
     
  5. Ernst,

    There is a pin, screwed inside the focusing ring, which engages a fork inside the lens, thereby coupling the ring to the focusing helicoid but allowing the helicoid to extend and retract while focusing--the pin slides in the fork. The pin once had a plastic bushing around it, which has now probably disintegrated. I have a lens with this problem.

    The pin is therefore too small in diameter to fit closely in the fork, so you get some rotational play. It is annoying, but it does not affect the actual focusing at all, only the feel of the ring and of course the indication on the focusing scale. It does not disturb the relationship of the lens elements.

    You won't need to heat the focusing grip. Use a somewhat sharp wooden or plastic object, work it under the edge of the rubber grip, and gently begin lifting and working around the ring. The grip will stretch enough to come off. It is held in place with a slightly tacky adhesive, which you will have to break loose. Do not attempt to turn the rubber grip inside out--you simply want to unstick it and stretch it just enough to slide it off of the lens.

    If I remember correctly, removal of the trim ring in the front of the lens (where the lens data is printed) will allow you to see the pin and the fork. Some of the rings screw in, and others snap in. I THINK this one screws in, but don't remember for sure. You could remove it to confirm the problem, but I'd bet anything it's the bushing decayed away.

    It does make precise focusing an annoyance!

    Good luck, and happy shooting.
     
  6. Hi Alan,

    many thanks for this detailed information!

    Just to confirm: If it were the problem that you describe (which sounds very plausible to me as it explains the play only in one dimension) there would not be a way to fix it. Correct?

    Cheers,
    Ernst.
     
  7. Hi Ernst,

    On a nFD lens, Mark is more than 99.9999% likely to be right, it'll be the screws under the focussing grip. What you describe is the early stages of the screws coming loose - they can't get any looser because of the rubber grip. This is a simple repair - one that I'd expect a camera tech to do in 5 minutes and as a freebie if you're already a customer.

    Mike.
     
  8. I would also bet on the bushing decay, but anyway you need to remove the rubber to access the screws... tighten the screws and you will see, if the looseness remains, you will have to replace the bushings!
     
  9. Thanks to all of you for your support!
    I removed the rubber and the screw beneth it was tightly fixed (actually all accessible screws are tight.

    So it's the bushing. Is there anything one can do about it (as to a possible replacement and a repair for an amateur like me)?

    Cheers,
    Ernst.
     
  10. I haven't opened a 2/35, but usually you have to unscrew these very same screws in order to desoliderise the external focus ring from the internal helicoid and remove the focus ring. Then you should actually see the bushings and be able to remove them.
    Replacement is another matter, I made do once with heatshrink tubing for electronics, but there are probably better sources.
     
  11. OK. Thanks to everybody. I keep you posted what happened after I will have opened the lens.

    Cheers,
    Ernst.
     
  12. Ernst,

    I haven't come up with a good substitute for the deteriorated plastic.
     
  13. I just bought a band.it instead, since its cheap and the focus ring will never wear out again, not to mention the better grip. They sell it on camerabandit.com
     

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