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  1. #11

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    Quote Originally Posted by Rlibersky
    Has anyone built a LF pinhole? I have some film that is 10.5in x 120ft. I am thinking of building a 10.5x18 inch camera. My question is should I make it so the film plane at the same distance from the pinhole on a circle or flat like it would be in a normal camera. When I 've used shorter length, ~300mm, pinhole on my 8x10 the edges seem to get distorted. Was this a function of a badly made pinhole?
    My completely unqualified opinion is that yes, you will need to make a curved back for the film plane to maintain the consistent distance from pinhole to film.

    Having said that, it also seems as though at these larger-than-usual dimensions the edge of the pinhole would really need to be clean. I think a pinhole with ragged ragged edges would be very obvious at that size.

    Also, if you missed it, scootermm had a similar project a while back.

    Nathan

  2. #12
    Rlibersky's Avatar
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    Thanks for the link. It inspires me to get out there and make it. I was thinking 300mm as well. And then doing wide angle street photography, mostly buildings of course, in Minneapolis.

  3. #13

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    Be sure to post anything you come up with. I've been shooting a lot of Nicollet Mall and some of Lake Street over in Spanish Harlem.

  4. #14
    Donald Qualls's Avatar
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    Quote Originally Posted by Rlibersky
    Has anyone built a LF pinhole? I have some film that is 10.5in x 120ft. I am thinking of building a 10.5x18 inch camera. My question is should I make it so the film plane at the same distance from the pinhole on a circle or flat like it would be in a normal camera. When I 've used shorter length, ~300mm, pinhole on my 8x10 the edges seem to get distorted. Was this a function of a badly made pinhole?
    Depends what you want. If the film is flat, you'll get the exact same geometry you'd get with a perfect lens and the same relationship of film plane to scene -- that is, if the film is parallel to the front of a building, you'll get no convergence in either verticals or horizontals. However, that looks very unnatural with extremely wide angles, because you're used to moving your head to view angles that wide and in doing so, your brain automatically compensates for the convergences.

    If you use a very wide angle, however, you'll also have significant exposure fall-off at the edges and especially corners of the frame; curving the film so the pinhole is at the center significantly reduces this fall-off, though it introduces distortion that, while looking very "normal" at the edges, leaves a strong curvature in what should be straight objects that cross the frame.

    Since pinhole cameras are so easy to make, why not do both? You can make a semicircular camera from a large popcorn tin or two gallon bucket, and a flat one from a wood box with a suitable film retainer in the back, and then see which you like. I'm betting you'll like both, for different things...
    Photography has always fascinated me -- as a child, simply for the magic of capturing an image onto glossy paper with a little box, but as an adult because of the unique juxtaposition of science and art -- the physics of optics, the mechanics of the camera, the chemistry of film and developer, alongside the art in seeing, composing, exposing, processing and printing.

  5. #15
    Rlibersky's Avatar
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    Donald thanks for the information. I think I will try both ways. After reading your statement about wide angles I figured the normal for this size film. A large 22 inches. I probaly will use a 18 inch focal length not a 12 inch.

  6. #16
    Donald Qualls's Avatar
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    A 12 inch with 22 being "normal" shouldn't be wide enough to cause a major problem with angles and size relationships being odd -- it'd be like a 21 mm on 35 mm film, approximately, decidedly wide but no fisheye. It will introduce considerable light falloff. You can calculate how much pretty easily -- use geometry to calculate the light path length from pinhole to corners, and then apply inverse square law to get a ratio of light level; each factor of 2x in light level is one stop, and fall off of one stop is quite noticeable, while two stops makes an image that's hard to print or reproduce.

    One of the wonders of pinholes is they can cover 120 degrees, if you can control the light fall off. Another is they keep everything in the same sharpness from 2-3 times the pinhole distance, out to the horizon. But the longer the focal length, the slower the pinhole (if you stay with something close to optimum, for which I use 1/25 of the square root of "focal" length, measured in millimeters), yet the fuzzier the image on the same size film, because the pinhole gets bigger as you move it away from the film, if you keep the optimum size. With huge film, however, you won't be enlarging, so you'll get a sharper print than you would with a "telephoto" pinhole on small film.

    Oh, yeah, one other thing to be aware of -- if you make a pinhole camera from a round can with the pinhole at the surface of the can, you'll get reflection lines (parallel with the can axis) in the image. If you make it with the pinhole at the center of curvature (essentially a half round), you'll get both more even exposure and no reflection lines (but be very sure to thoroughly blacken the inside of the can and the film side of the pinhole itself, since light from the hole will reflect back to a line through the hole and parallel with the can axis, causing flare).
    Photography has always fascinated me -- as a child, simply for the magic of capturing an image onto glossy paper with a little box, but as an adult because of the unique juxtaposition of science and art -- the physics of optics, the mechanics of the camera, the chemistry of film and developer, alongside the art in seeing, composing, exposing, processing and printing.

  7. #17
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    I once when looking around an abandoned building here in auckland found a room that had the image from outside cast on its wall projected from the hole left in the door from the lock...

    We filmed it for a while, nice distortions as the wall wasn't perpendicular with the plane of projection

  8. #18
    Rlibersky's Avatar
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    I finally got a 10"x20" made. A box inside a box. 14" lens to film distance. Looked at what I wanted to cover and found this was the best combination. Now I have to figure the best size hole. Any suggestions?

  9. #19
    Sandeha Lynch's Avatar
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    The largest I've heard of was 2mx32metres. Yup, 32 metres of black and white printing paper tacked to a wall, developed by a team of workers using buckets and sponges ... (Simon Read, Roundhouse, London, late seventies) ... they don't make them like that any more. OK, so it wasn't portable

  10. #20
    Donald Qualls's Avatar
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    Quote Originally Posted by Rlibersky
    I finally got a 10"x20" made. A box inside a box. 14" lens to film distance. Looked at what I wanted to cover and found this was the best combination. Now I have to figure the best size hole. Any suggestions?
    Overall, the optimum hole size (for best image sharpness) is generally found by dividing the square root of the focal length by 25, all measurements in millimeters. For 14 inches, that would give SQR(356)/25 = 0.75 mm, or about .030" diameter, which in turn will give f/470, about.
    Photography has always fascinated me -- as a child, simply for the magic of capturing an image onto glossy paper with a little box, but as an adult because of the unique juxtaposition of science and art -- the physics of optics, the mechanics of the camera, the chemistry of film and developer, alongside the art in seeing, composing, exposing, processing and printing.

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