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  1. #1

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    Maximum negative size vs. Aperture vs. focal length?

    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. #2
    Nicholas Lindan's Avatar
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    Sep 2006
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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.
    DARKROOM AUTOMATION
    f-Stop Timers - Enlarging Meters
    http://www.darkroomautomation.com/da-main.htm

  3. #3

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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.



 

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