Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 71,531   Posts: 1,572,516   Online: 1081
      
Page 1 of 2 12 LastLast
Results 1 to 10 of 16
  1. #1

    Join Date
    Jun 2013
    Location
    Stockton, CA - USA - EARTH
    Shooter
    35mm
    Posts
    82

    lens assembly help needed

    I decided to tear apart my cheapie Sigma 28 f/2.8 mini-wide today because something condensed on the elements inside. I wasn't too concerned, I've pulled lenses apart before and frankly wasn't going to be to upset if I screwed up this lens.

    I got things cleaned up and mostly reassembled, but am having difficulty with the foucing ring. The inner group has th coarse thread for focus, there is a reverse thread lock ring that the focus ring attaches to. The inner group and lockring to body is where I'm having trouble. Anyone have ever dealt with these? Anyone have service instructions? Or know where I can find them? This lens isn't worth having a pro work on, I'm not ready to throw it in the trash yet either.


    -Xander

  2. #2

    Join Date
    Jul 2010
    Location
    Southern USA
    Shooter
    Multi Format
    Posts
    4,063
    Too late to help now but for future reference professional repairers make small scratches on internal parts to show the alignment of various components. You often see them when repairing old lenses.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

  3. #3

    Join Date
    Jun 2013
    Location
    Stockton, CA - USA - EARTH
    Shooter
    35mm
    Posts
    82
    ...yeah...


    -X

  4. #4
    David Lyga's Avatar
    Join Date
    Nov 2007
    Location
    Philadelphia, PA USA
    Shooter
    35mm
    Posts
    1,309
    it is so difficult to pinpoint just what you are trying to say, Fast, but I have taken apart many of this type. One thing to remember with 28s (and wider) is that the direction of the many elements is of paramount importance and you MUST make notes of what you are doing as you disassemble. Perhaps in your case you left the individual sets of element intact. Then you will have no problems with what I just said.

    I get the fleeting impression that your problem is with the helicoid. You must re-enter the helicoid (where the individual coarse threads mate) at the correct point. There is a (brass?) ring that has fine threads on the outside for screwing onto the lens body and coarser threads on the inside which mate to the coarse threads on the front element group. It is difficult to explain precisely in your case as there is variation with the different off market 28s out there, but you must make sure that, when fully threaded, you are able to focus to infinity. Call me if you think that I might be able to explain more fully. No promises. 215.569.4949 - David Lyga

  5. #5

    Join Date
    Jun 2013
    Location
    Stockton, CA - USA - EARTH
    Shooter
    35mm
    Posts
    82
    David, yes its the helicoid and ring that attaches it to the body that's giving me fits. I'll have to get in touch with you tomorrow as I am working and the time difference between us would make I too late to call. In the mean time I can take some pictures of exactly where I am having trouble and email them to you so you can see what I am dealing with.


    Thanx!

    -Xander

  6. #6
    David Lyga's Avatar
    Join Date
    Nov 2007
    Location
    Philadelphia, PA USA
    Shooter
    35mm
    Posts
    1,309
    Try any hour. I disconnect my phone when I am sleeping. You will NOT bother me. But, again, no promises. Hint: you just might get me at 5-6 AM EST. - David Lyga

  7. #7

    Join Date
    Sep 2008
    Shooter
    Multi Format
    Posts
    795
    The helicoid will mate up at several locations. You have to try them all to make sure you get the right one.

  8. #8

    Join Date
    Jun 2013
    Location
    Stockton, CA - USA - EARTH
    Shooter
    35mm
    Posts
    82
    Yeah, that seems to be the issue I'm running into, I was hoping there was a reference measurement or something. I'll try that out and then possibly give David a call.


    -X

  9. #9
    David Lyga's Avatar
    Join Date
    Nov 2007
    Location
    Philadelphia, PA USA
    Shooter
    35mm
    Posts
    1,309
    Sometimes the 'mating' can be different from what it was when you initially took it apart because on some lenses there is an ability to set the focus at different points of the helical turn and match this new turn with the proper point on the focus ring.

    Actually, you probably did not have to remove the helicoid; you maybe could have simply unscrewed the front and rear element sets. On some 28s that is so. But I usually do remove the helicoid because this gives me an opportunity to remove all the black gunk with lighter fluid and a brush, then re-lubricate with a tiny bit of Vaseline petroleum jelly. Most lenses have too darn much of this lubricant and ONLY NIkon was sparing in its application. That's why the focus on its lenses rarely stiffen with age. - David Lyga

  10. #10

    Join Date
    Apr 2004
    Location
    Montgomery, Il/USA
    Shooter
    Multi Format
    Posts
    5,255
    Unfortunately the helical must be correctly aligned.
    If it's not correct, the lens may extend either too far allowing the helical to separate or; the flip side to this coin is the inability to focus closer than infinity.
    The focusing ring being able to move 360 degrees as used in inexpensive lenses to allow the ring to be adjusted to the focus index on the barrel.

    Vaseline may work(?) so does wheel bearing grease or possum fat, but a white grease is a correct solution.
    Heavily sedated for your protection.

Page 1 of 2 12 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  —   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin