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  1. #11

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    Good Morning, Dan
    That photo is with the lens newly modified, that is, reversed from its original orientation.
    Note that the "lens board" was , and will be, in front of the lens, as shown in the photo of the original camera.
    Originally the nameplate end of the lens was attached to the lens board.
    With my mod, the nameplate end of the lens will point to the film.

    With search in my spare time, I found a generic prescription for the speed panchro ( 6 glass, double gauss)
    I am modeling that in OpticalRayTracer. Of course I don't know if the model is the same as the Oscillo.
    But the focal length is 77mm and the dimensions are close to what I can measure on the real Oscillo

    Still working on it, but so far it seems that the lens would need to be reversed to cover the original Polaroid at 1:1 .
    When the reversed lens is focussed on infinity the spherical abberation is bad., but the image circle is more than 100mm at 1:1

    When I flip the lens model to its correct orientation the image circle reduces to about 38mm radius (76mm dia)
    Then the spherical is well corrected ( within 200 micrometre or so) from the film plane, between axis and 38mm radius.

    So that leads me to wonder if the Oscillos lens was just a variant of a standard Speed Panchro medium format lens, but reversed in the shutter by swapping the shutter threads between front and rear .
    Do you think that is feasible?

  2. #12

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    Mar 2005
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    Small surprise of the day. I have a set of 75/1.9 Oscillo-Paragon cells -- actually, I have two of 'em -- and several Ilex #3 shutters. So I did the obvious thing, tried to screw a rear cell into the front of the shutter. It won't go, hits the diaphragm before the threads engage. So much for that.

    Speed Pancho is a TTH trade name that includes a number of different prescriptons, all 6/4 double Gauss types. I refer to the type as 6/4 double Gauss to avoid pointing at a particular and very good lens. There are many, many 6/4 double Gauss type lenses, some better than others.

  3. #13

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    Progress on this thread (Its a spare time thing):
    I have made a "flying test bed" 6x7 body out of the old O_ER camera parts, it is "thin" as suggested by Dan Fromm.
    So there is plenty of room up front to mount experimental lenses on a machined adaptor plate set up.

    Here is a raw image with the Oscillo lens on Fuji 160. .... Yikes.
    https://app.box.com/s/4tnhnaytrml2vtfpbxxg

    It does not quite cover the 6x7. But worse , it has severe pincushion.
    With some reading and using Imagemagick functions , I think the distortion is of the third order with radius. So the distortion is not so obvious near the axis but gets bad at the edges because it grows with 3rd power of radius
    Here is the above image that has been partially corrected for 3rd order distortion by "convert" function and tca by "tca_correct" , and cropped to 5x5 square. ......But still Yikes.
    https://app.box.com/s/gl0zrlu7aohiwdj8k395

    There is nothing more I can do with the Oscillo so I pulled it off and now making an adaptor for a Takumar 6x7 bayonet, as I have the Taks 6x7 55, 75, & 90mm.

    That brings me to the old Ilex #3 shutter.
    It had a lot of wear in the hole that mounts the firing lever on its spindle.
    I can't imagine how a manual Polaroid camera could have a worn shutter.
    I have corrected the problem with an M3 washer so the shutter works and later I will drill the lever and make a brass bush in the lathe to fix it.
    The other parts of the shutter look clean and in good shape, and the timing is reasonably OK.

    The shutter will have to be reverse mounted to just clear the image cone of the Takumar lenses.

    I will put up some photos when( and if !!) it is working OK.

    regards,

  4. #14

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    Wombat, thanks for the update. Thanks too for confirmation that 'scope camera lenses aren't the answer to an aging photographer's prayers.

    Cheers,

    Dan

  5. #15

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    Thanks Dan,
    I have learned that the "lens bench" approach is no way to test a lens.
    For testing a lens there is no substitute but for taking a real photo with the lens properly aligned and light tight

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