Barry you just killed pinholes for me. God why do you people have to be so damn technical about everything? To me the beauty of a pinhole is in the soft image not another technical excersice is getting the perfect super sharp image creating pinhole. I use a regular lens for that.
I just use a PIN and put a HOLE in some metal and put that on a box or a tube and have fun. Getting out the microscope to measure the hole just takes all the fun out of it for me.
I didn't say you had to. So poke holes in foil with a pin and have fun.