DIY AI conversions

Discussion in '35mm Cameras' started by DD (Rox), Sep 19, 2005.

  1. DD (Rox)

    DD (Rox) Guest

    I have just been reading up on some of the AI conversion websites and I
    was wondering if it wouldn't be easier to swap out aperture rings from
    older MF lenses with rings from "retired" newer lenses?

    For example, I just picked up a mint 50mm f/1.4 non-AI lens and instead
    of butchering the lens with a file to get it to mount on a D70, I wonder
    if it wouldn't be easier to just get a stuffed up AIS 50mm and exchange
    the aperture rings? Are the machined couplings hugely different?

    I also picked up some other bargains at the same time, namely a Minolta
    Auto Meter and a minty Nikon 80-200mm f/4 AIS. The zoom is perfect
    except for a small blotch of fungus on the front element. I shot a bit
    with it yesterday and was amazed to see just how sharp it is wide open
    at f/4.

    The Minolta Auto Meter looks great too and is way cool to use, providing
    you with all the possible shutter speed / aperture combinations at a
    single reading.
    DD (Rox), Sep 19, 2005
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  2. I can't really answer the question directly, but here are some things to
    ponder. Nikon made AI lenses that were the same as the NON-AI versions
    only for a few months. By the time auto-indexing was announced, they had
    switched to the rubber focusing rings and multicoating.

    The non-AI versions of these lenses were only made for a few months and
    IMHO, too rare to convert now. If you have one in good shape, a
    collector might value them more than a good condition AI lens.

    My guess is that if you could get a ring to fit it would work. The problem
    would be to find an exact match. A better idea would be to try and find a
    broken pre-AI lens that had an AI apeture ring fitted, aka "factory AIed".

    Since all of this occured almost 30 years ago (mid 1977), it may be difficult.

    Note that you cannot AIs a lens. The "s" indicator, a small indented
    area on the lens does not actualy do anything except tell the camera
    that the diaphragm follows the "s" specifications. Making the indent
    does not change the diaphragm, and could result in widely inacurate

    It came about because the first "programed exposure" Nikon, the FG,
    could not tell where the diaphragm would be when it stopped it down.
    So it would close the diaphragm to where it wanted it to be and then
    reevaluate the exposure based upon the actual reading.

    This gave you correct exposures as long as you had not metered on an
    object and moved the camera, but it often did not give you what you

    In order to prevent this problem, NIKON "tweaked" the design of the
    diaphragm stop down mechanism to be repeatable across it's range of
    lenses. Moving the stop down lever the same amount, would yeild exactly
    the same proportion of closure on any lens you would mount.

    The indicator on the back told the camera that this lens followed the
    specification and could be used for programed exposures. AFIK, the first
    camera to use it was the FA.

    If the D70 uses AIs lenses and not AI, then it would be a waste of
    time and money to try to manualy AI a lens.

    Geoffrey S. Mendelson, Sep 19, 2005
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  3. DD (Rox)

    Matt Clara Guest

    Would it be worth the trouble? John White of Ann Arbor charges something
    like $35 including shipping.
    Matt Clara, Sep 19, 2005
  4. John White of AIconversions can make it an AI lens for about $40....If all
    you want to do is mount it, you can just remove the little "bat wings" with
    a tiny phillips screwdriver.......On a lot of cameras, the lens will mount
    OK anyway....
    William Graham, Sep 19, 2005
  5. DD (Rox)

    Gordon Moat Guest

    There were some changes from five screw to three screw fittings for the
    mounting and aperture rings. The change to AI also meant some of the
    machining was different. It might be possible on a few lenses, but not

    The 50 mm f1.4 AIS was the best of the 50 mm f1.4 choices. These are also
    very common and not very expensive. You gain little in trying to use an
    older non-AI 50 mm f1.4. The 55 mm f1.2 is the only one I can think of that
    might be worth converting in the standard or near standard focal length.
    The Nikkor-S version of that 55 mm is actually quite a nice lens, though
    not like the Noct version.
    I was never a big fan of those, but if you like it then that is good.
    Should be fairly reliable. It might change some of your shooting habits.
    Gordon Moat, Sep 19, 2005
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