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Help: Zeiss Jena 25mm f1.4 Tevidon

Discussion in 'Adapted Lenses' started by Dannysaur, Dec 28, 2015.

  1. Dannysaur

    Dannysaur New to Mu-43

    2
    Dec 28, 2015
    Daniel
    Hi all,

    Made an account just to ask for some help.

    I've had a 25mm f1.4 Carl Zeiss Jena Tevidon for a few years now, and I've been trying to adapt it for MFT. Have infinity focus issues a Metabones adapter. After digging around, it seems as though this lens needs a little bit of machining so that the lens can sit flush against the adapter to get to focus to infinity.

    Question is: how do I go about getting this lens surgery done? What should I tell a machinist I need done? Is it possible to do it myself by sitting down and just filing it down with a metal file? Just looking for some advice here.

    Thanks,

    Dan PC281527.JPG
     
  2. barry13

    barry13 Super Moderator; Photon Wrangler

    Mar 7, 2014
    Southern California
    Barry
    Hi & welcome,
    Which mount is this lens?

    Barry
     
  3. phigmov

    phigmov Mu-43 Hall of Famer

    Apr 4, 2010
    Seems like a c-mount ? Can you modify the adaptor instead ? Maybe get some cheap adaptors and play around with different cuts.

    I'm always wary of modifying lenses. Although if there are some spacers screwed onto the back plate, perhaps you could remove those so at least its a non-destructive alteration ?

    How much distance do you need to shave off ?
     
  4. Dannysaur

    Dannysaur New to Mu-43

    2
    Dec 28, 2015
    Daniel
    Hi guys, thanks for replying.

    I have a metabones C-mount to MFT adapter, as well as a cheap one I got off Amazon. Modifying the adapter might be a bit more difficult than modifying the lens, due to the adapter being so small.

    I don't really know how much I have to take off, just enough that it the lens can sit flush against the back of the adapter. The back screws are in the way though

    PC281528.JPG
     
  5. phigmov

    phigmov Mu-43 Hall of Famer

    Apr 4, 2010
    Ulfric cut back a lens from a Yashica fixed-lens film camera a few years back - might give you some ideas -

    Yashica GSN Butchery
     
  6. Klorenzo

    Klorenzo Mu-43 All-Pro

    Mar 10, 2014
    Lorenzo
    First thing should be to really understand what part need to be filed. The large black outer border, the inner metal ring, etc.
    You could try to paint it with a black marker or something like that and see where it gets removed.

    If you think is the black large ring you could try just to remove it completely, mount the lens and see if it solves (I suppose it is just a protective cover, not holding parts in place).

    I would also prefer to modify the adaptor. You could also take precise measurements with a caliper (1/10 mm) of the lens and adapter and ask about it to Metabones. I suppose both should have very strict tolerances.

    Then be sure that the lens does not reach infinity focus at all rather then going beyond infinity: opposite problem.