# Maximum negative size vs. Aperture vs. focal length?

• 08-28-2012, 05:25 PM
subbreydon
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?
• 08-28-2012, 06:43 PM
Nicholas Lindan
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.
• 08-28-2012, 07:37 PM
sneebot
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.