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Thread: 11x14 or 8x10 box type camera

  1. #11

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    Re: 11x14 or 8x10 box type camera

    Well, the focal length of the pinhole would be the distance from the pinhole to the film. When you read Renner's book, you will find a chart of optimal pinhole diameters for given distances to the film. If you know the diameter of the pinhole and the distance from the pinhole to the film, you can calculate your f/number. It's all in the book.

    Peter Gomena

  2. #12

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    Re: 11x14 or 8x10 box type camera

    I have only dabbled with a few pinhole cameras and shots, so I'm no authority on them, but google pinhole cameras. This link was quite handy to me: http://www.mrpinhole.com/calcpinh.php

    Edit to add link to pinhole site: http://www.f295.org/site/

  3. #13

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    Re: 11x14 or 8x10 box type camera

    Quote Originally Posted by bvaughn4 View Post
    I have only dabbled with a few pinhole cameras and shots, so I'm no authority on them, but google pinhole cameras. This link was quite handy to me: http://www.mrpinhole.com/calcpinh.php

    Edit to add link to pinhole site: http://www.f295.org/site/
    I noticed that the image circles given by that calculator differ from Peter's 3.5x rule of thumb above. The calculator gives 240mm FL to get a 450mm image circle.

    Don't know which is correct, the difference may be down to different definitions of "coverage" (falloff tolerance)

  4. #14
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    Re: 11x14 or 8x10 box type camera

    Quote Originally Posted by Peter Gomena View Post
    Well, the focal length of the pinhole would be the distance from the pinhole to the film. When you read Renner's book, you will find a chart of optimal pinhole diameters for given distances to the film. If you know the diameter of the pinhole and the distance from the pinhole to the film, you can calculate your f/number. It's all in the book.

    Peter Gomena
    Great, can't wait to get it.


    Quote Originally Posted by bvaughn4 View Post
    I have only dabbled with a few pinhole cameras and shots, so I'm no authority on them, but google pinhole cameras. This link was quite handy to me: http://www.mrpinhole.com/calcpinh.php

    Edit to add link to pinhole site: http://www.f295.org/site/
    What a need site, that mrpinhole! Thanks!

  5. #15

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    Re: 11x14 or 8x10 box type camera

    Is the shape of the pinhole that important? Skink pinholes are done with a laser which is supposed to better because the hole is more round that using a needle. Is that true? I'm thinking of doing something similar, and wondering if I can adapt their system and if it would be a good idea.

    Edit: This or this would do it, but are they really better?

  6. #16

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    Re: 11x14 or 8x10 box type camera

    Laser-drilled pinholes are fine, but it's not difficult to make a good, round pinhole. You can buy a lot of thin brass sheeting for the cost of one laser pinhole. It does take some practice, but there are good resources on-line on how to drill a pinhole yourself. I found it helpful to have a transparent printer's gauge that I could put on the end of a loupe to measure the diameter of the pinhole. You can estimate pretty accurately from there.

    Yes, the 3.5X focal length is a rule of thumb. A 120mm focal length pinhole will cover 8x10". The central 5 inches of the image are much sharper than the outer portions, and there is a little light falloff toward the edges, but it's not extreme.

    See Eric Renner's website at http://www.pinholeresource.com for laser pinholes, lens cap pinholes, and pinhole cameras.

    Peter Gomena

  7. #17
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    Re: 11x14 or 8x10 box type camera

    You are describing an image I can only desire, Gomena

    Kurtdriver, those look interested too. If one wanted to do pinholes on a real camera, I think they would be nice to have quality-feel-wise.



    Quote Originally Posted by pbryld View Post

    What a need site, that mrpinhole! Thanks!
    Whoops, meant 'neat' obviously.

  8. #18
    JoeV's Avatar
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    Re: 11x14 or 8x10 box type camera

    The thickness of the pinhole material has some effect on light falloff.

    A theoretical pinhole of zero thickness will have light falloff as per the cosine^4 function, due to the effects of increased distance to the pinhole, and because the aperture is being viewed increasingly as an ellipse away from the central axis.

    Now add the thickness of the pinhole material into the equation and you can see the pinhole is really a shallow tunnel; if the tunnel is deep enough (i.e. the material is too thick), the off-axis view of the pinhole as being an ellipse becomes truncated by the walls of the tunnel, further reducing light throughput, leading to some vignetting in the corners, perhaps, if the material is of sufficient thickness.

    EDIT TO ADD:
    The relationship between focal length and film size is helpful in determining the camera's angle of view. Generally, if the focal length is around the size of the film's diagonal width, it will have a "normal" angle of view, and exposures will be more even across the image between center and corners. As you increasingly shorten the focal length in relationship to the film size, more light falloff and vignetting occur.

    Imagine an infinite pinhole camera, one where the film plane extends outward in all directions. Whatever distance you place between the pinhole and this infinite film plane, the image circle formed will gradually fade away to black as you get further in angle away from the centerline of the system. Now crop this infinite film plane down to some finite size and you can see that your choice of focal length together with film size determines how much off-axis light falloff.

    Regarding camera design, I've taken to building box cameras out of black foam core board and black gaffers's tape (not black duct tape but the real gaffer's tape), small enough to fit within a changing bag. The camera has a lid that slides off when inside the changing bag, where inside the camera, behind the film plane, is a storage compartment for many dozens of sheets of paper, enough for a vacation's worth, if needed. The camera is reloaded, out in the field, between shots.

    For an ULF version of this idea (like 11x14), you'd have to employ either a changing tent (the kind used for reloading LF film holders), or build arm sleeves into your box camera to permit the paper to be directly reloaded while out and about.

    Sheet film holders, while a great convenience for cycling through many shots, can be fairly easy to carry in the 4x5 size, but a stack of even four 8x10 holders can weigh as much or more than an 8x10 foam core box camera in its entirety. For 11x14 cameras, carrying sufficient numbers of sheet film holders becomes impractically expensive and cumbersome. If I were spending that much money on such ULF film holders, I'd build a high-quality lens camera system around them instead. For pinhole, keep it simple and inexpensive. My "storage slot" box camera concept, reloaded inside a changing bag, is a practical and inexpensive compromise.

    -Joe
    The photograph and the thing being photographed are not the same thing.

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