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  1. #1
    krisbfunk's Avatar
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    multi slit pinhole camera

    Hi,

    I'm planning on designing a 4x5 multi slit pinhole, with two slits, one vertical and one horizontal, spaced a few centimeters apart from each other so all the film sees is one square pinhole. Has anyone attempted this?

    I've found limited information on it, but it has been done and the results are very interesting, with a perspective skew due to the focal length difference. The thing I'm not so sure of is the distance between the pinhole plates before major blurring occurs.

    Any info would be appreciated. Thanks.

  2. #2
    DBP
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    I haven't seen it done with slits, but Marcy Merrill has done some interesting work with multiple holes.

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    krisbfunk,

    It would help if you could describe your intended application. Do you intend to keep the two slits perpendicularly crossed against each other? I have some experience in making and using a two-slit camera (120 format), and have had very interesting results from rotating S-shaped slits against each other. I set the slits at various positions, but not at right angles to each other, because to do so would make the slits function as a square-shaped pinhole. I designed the camera primarily to work with distorted images.

    I have one slit at 75mm from the film plane, and the other at 150mm, or a ratio of 1:2. This ratio introduces a fixed amount of distortion in the images made by the camera. The direction of the distortion (or how the image is "pulled" towards one side or the other) is a function of the relative orientations of the two slits.

  4. #4
    krisbfunk's Avatar
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    i found some good direction in this pdf (page 11)

    www.stanford.edu/~cpatton/pinhole/cpbeyond.pdf

    "The vertical slit determines the horizontal focal length and vice-versa.
    The width of the opening of the slits is the same as the ideal pinhole diameter. Remember the front and back slits are at different distances/focal lengths.
    The length of the slit is determined by were it is in relation to the opposing slit and is determined easiest by looking."


    and it states in the directions of a 4x5 pinhole for front panel options: (c)

    "a) Straight pinhole designs, zone plates and hyperfocal cameras
    b) Multiple holes, overlapped and separated
    c) Double slit and double zone
    Two front panels needed [pinhole side]. The second panel is
    recessed into the interior of the box the desired amount for the
    second focal length. The measurements of the box will be based on
    the longest focal length used."

  5. #5
    krisbfunk's Avatar
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    OK, here is the double slit pinhole page in HTML

    http://pinhole.stanford.edu/ds.html

    And here are the optimal slit widths for a 4x5 double slit camera

    http://pinhole.stanford.edu/dsm.htm

    So I'm assuming the a:b section is in inches as well, in the first section slit a is 1 inch, and slit b is 2 inches. correct me if i'm wrong.

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    It looks to me like A:B is describing the ratio of distances of slit A and slit B to the film plane. So if slit A is 2 inches from the film plane, then slit B is 4 inches for a 1:2 ratio. The ratio is unitless.

    Have you had a got at this?

  7. #7
    krisbfunk's Avatar
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    That sounds more like it, and is exactly what I was wondering. I have the camera designed and is in the black tape process . I'm planning on using laser transparencies for the slits that i designed in Illustrator, hopefully the black will be dense enough.



 

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