Maximum negative size vs. Aperture vs. focal length?

Discussion in 'Pinhole Photography' started by subbreydon, Aug 28, 2012.

  1. subbreydon

    subbreydon Member

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    I want to make a wide-angle pinhole for solargraphs. I have read about a plan for a matchbox pinhole that has an angle of view of about 160 degrees and I wanted to achieve that same range of view, but be able to use 8x10 BW photo paper. If I made a camera with a focal length of about 6-15mm, would I be able to achieve a similar angle of view without an unholy amount of vignetting? Is there a specific formula to find out the maximum negative size in proportion to the focal length and pinhole size before vignetting occurs?
     
  2. Nicholas Lindan

    Nicholas Lindan Advertiser Advertiser

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    15mm pinhole and 8x10 image???? Be prepared for a truly hole-y amount of vignetting.

    Falloff follows a cos^4 for an ideal pinhole.

    For 160 degrees, the half-angle is 80 degrees, cos(80)^4 = 0.0009 = 10 stops down.

    But you probably won't be able to get even that unless your pinhole is made in a material that is infinitely thin.
     
  3. sneebot

    sneebot Member

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    Using a cylinder type camera you should be able to get very even exposure and 160* angle of view. Focal length (at center) would be closer to 4".

    Here are some 57 I made:
    http://www.flickr.com/photos/sneebot/3643265909/

    Also made a 810 version but haven't used it much.