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Thread: Crazy lens idea - an experiment.

  1. #1
    Les
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    Crazy lens idea - an experiment.

    Howdy,

    I was just wondering (might be too much time on my hands) if it's at all possible to adopt this 28-80mm F3.5/5.6 Pentax lens (35mm type) to a 4x5 rig. I don't care if the zoom is not usable, since I'm thinking to take it all apart and use individual lens pieces. I have no problem with butchering it since I got it for nearly no cash. Just wondering if I'll even get an image....and what sorts of gadgets would it take to align the glass pieces. Thanks to those that can offer some useful findings/advise.

    Les

  2. #2

    Join Date
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    Re: Crazy lens idea - an experiment.

    My first guess is that the image projected behind the lens will be too small in diameter to cover a 4x5 sheet of film....

    --Darin

  3. #3
    Foamer
    Join Date
    Oct 2010
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    South Dakota
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    Re: Crazy lens idea - an experiment.

    Those zoom lenses like that have about a half million pieces. I don't see any way to align them. I also don't see how you could get them to focus.


    Kent in SD
    Qui sedes ad dexteram Patris,
    miserere nobis.

  4. #4

    Join Date
    Jul 2007
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    Austin TX
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    Re: Crazy lens idea - an experiment.

    Indeed, the issue is that you'll need to scavenge those pieces of glass that individually or in concert have a much longer focal length than the full group 35mm format. That may be only one simple element or if you're lucky maybe an achromat from somewhere in the mix. An accurate layout of the elements would give you a hint - identify the lens and give Google a shot. There is a lot of activity on older 35 mm SLR lenses.

    Nate Potter, Austin TX.

  5. #5
    ic-racer's Avatar
    Join Date
    Feb 2007
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    5,692

    Re: Crazy lens idea - an experiment.

    Quote Originally Posted by Leszek Vogt View Post
    Howdy,

    I was just wondering (might be too much time on my hands) if it's at all possible to adopt this 28-80mm F3.5/5.6 Pentax lens (35mm type) to a 4x5 rig. I don't care if the zoom is not usable, since I'm thinking to take it all apart and use individual lens pieces. I have no problem with butchering it since I got it for nearly no cash. Just wondering if I'll even get an image....and what sorts of gadgets would it take to align the glass pieces. Thanks to those that can offer some useful findings/advise.

    Les
    If you are thinking of a single-lens ordeal that may be possible. Just hold each of the positive elements up to a white board and see if any will project an image that covers 4x5. Perhaps something like a 2 diopter strength element.

    If you were wanting to have just the little circle in the middle of the 4x5 sheet, you will probably need a recessed lens board to focus the lens as a unit.

  6. #6

    Join Date
    Nov 2008
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    Atlanta, GA
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    652

    Re: Crazy lens idea - an experiment.

    Sounds like you might get a component or two you could use to make a simple soft focus lens.

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