I am attempting to recover from a deep seated addiction to commercially drilled pinholes. My research yields the following, which I will share because I have never seen it written anywhere before. Exposure time for any given pinhole doubles with each 40% increase in diameter, but sharpness of image with changes in pinhole diameter degrades much more slowly, and requires quite drastic increases in pinhole diameter to give significant changes in sharpness. I've done some testing to confirm this, but the best example of this is on page 128 of Eric Renner's book. You can see some increased softness of the image with a pinhole twice as wide as optimal, but you really don't begin to lose detail until the pinhole is between three and four times as wide as optimal. Even a pinhole ten times as wide as optimal will yiled a very readable image. In Eric's example pick an arbitrary focal length and divide the various fstops shown in the illustration into it. You will see the ratios of aperture diameter associated with different degrees of sharpness. Thus the error associated with using one size needle or another, over a wide range of focal lengths, is negligable (sp?). One will get surprisingly uniform sharpness and clarity of the image with any pinhole, because the difference in pin diameters for different numbers of needle is far less than 100%. Many of you have taken this for granted but here is a way for the precision technonerds to see a way to loose their chains.
