Thanks for the explanation about the focal ratio. The camera I'm using now has a .46mm aperture, and a focal length of 190mm - works out to f/413 (I think you saw one of the images made with it in my other thread about the size of the camera). The pinhole should be larger but I found that when I used the optimal pinhole size for the focal length it became too unsharp for my liking. I swapped it for another pinhole I made for a shorter focal length camera.
Originally Posted by Joe VanCleave