Optimal pinhole diameter is a matter of taste, like seasoning on food. I prefer Pinhole Designer with a user constant of 1.4 when determining pinhole size. This yields a diameter of .383 for a 136mm focal length on film. This choice is based on many resolution tests. Some adjustment of the diameter for pictorial photography might suit others better. The shorter the focal length (and thus the smaller the pinhole) the sharper the image. Pinhole cameras are more suited to wide angle photography than normal or longer focal lengths. Larger pinhole cameras can record more detail for a given angle of coverage. There is a wealth of information on http://www.f295.org/Pinholeforum/forum/Blah.pl
Originally Posted by aterimagery
Hardware stores sell brass shim stock in thickness from .001 inch up. .002" is a good comprovise between thinness and ease of working. A few dollars spent on brass shim stock should last a lifetime.