You don't really focus a pinhole as you would a lens. You just set it at some distance from the film, which is your focal length. All things are equally sharp from near to far, but none are perfectly sharp. You can get your focal length by measuring, and you can change it with the focusing rack. You also can measure the size of the pinhole, and a given pinhole can serve for a range of focal lengths, dependent on your tolerance for unsharpness. Focal length divided by pinhole diameter gives your f-stop (when measured in like units).
Originally Posted by waynecrider
An old Graphic makes a great pinhole camera.