DIY Zenitar MC 16mm fisheye conversion to OM mount

Discussion in 'Olympus' started by ondrejp_spyderman, Sep 25, 2008.

  1. Zuiko fish eye is expensive, Sigma hard to find, but the russian Zenitars are readily available... Only problem
    that the Zenitars are made in Canon EOS, Nikon F and M42 mounts.

    I happened to have one Zenitar at home, and also a Zuiko 50/1.8 MiJ infected with fungus. Both of these lenses
    have easily removeable mount. They can be relatively easily swapped (with some drilling of the OM mount to fit
    the holes on the Zenitar lens). It's really not a difficult to do modification if you use the original M42 mount
    as template for the holes.

    This way the lens physically fits OM camera, but:
    a) cannot focus at infinity (mine could only reach to about 1m)
    b) metering does not work

    I don't have a solution for the metering, but it is very easy to get it to focus at infinity. (even without this,
    the DOF will reach to infinity at f/8 and smaller aperture) To reach real infinity focus, the optics has to be
    moved closer to the film plane. To do this I had to remove the rubber on the focus ring, loosen 3 setscrews (to
    disconnect the focus ring from the optics) and move the focus ring so as to enable the optics to focus farther
    than before (to enable the optics to go closer to the film).

    I did this and voila - I've got a OM-mount fish eye.

    I will post pictures of the lens, and from the lens later.
  2. Brilliant! Thanks very much Ondrej. I had just such a problem myself.

    I bought one of the lenses, supplied with a Canon FD adapter but wanted to use it on my OMs.

    I tried to obtain an M42 converter but all on eBay turned out to be T-mounts. That is, until I obtained a genuine M42 adapter. That has the infinity correction lens at the rear, good news for focus but bad news for the lens: the 42mm thread is too long and it won't screw in far enough to have any useable range of focus.

    I considered the replacement of the baseplate but have hesitated. Now you have made the move first and shown me what to do. (I assume that your lens is not obstructing the mirror).
  3. One question: The FD adapter has a special ring which pushes the diaphragm pin of the lens inwards to close the diaphragm down to the aperture selected. How do you provide for diaphragm operation in your set-up?
  4. Hi Harold,

    the lens isn't obstructing the mirror. The rear element protrudes less than the rear element of Zuiko 50.

    The diaphragm stop-down pin can be easily removed once you open the back of the lens. Without the pin and its mechanism the lens is completely manual i.e. it directly sets the aperture when you set it on aperture ring.

    I've just come home, so I'll take some pictures of it.
  5. Here is the replaced lens mount....
  6. And the rear element - almost fluch with the rear of the lens.
  7. Very cool hack... there's also an 8mm Peleng fisheye that is made in OM mount, but read much about it's quality.
  8. Dear Patrick, I'm not sure they are really OM mount. As far as I know RuGift as well as some ebay sellers sell "Zenitar for OM" or "Peleng for OM", but in fact it's usually the M42 version with adapter. But I may be wrong...
  9. Ondrej,

    Thanks for the additional details. I had assumed that the pin had a positive, not a negative effect on diaphragm closure. If auto diaphrgm can be dispensed with from any type of lens it is with a fisheye!
  10. Your next conversion project?
  11. :D LOL

    Definitely! Just buy it and send it to me ;)
  12. Your skills might be the key to much wider use of a unique lens of restricted application:

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