I made a protoype camera consisting of a pinhole with a crystal ball placed
outside the camera in front of the pinhole. I wanted to capture a sharp,
inverted and distorted image appearing within the crystal ball. But the
image was fuzzy. I think if I place the crystal ball further away, the image
sharpens. Can anyone give me a simple formula for the focal length of a
spherical lens, or whatever the terms are, to get a sharp image? I've tried
every optics text I can understand, which is a minority of them, but nobody
talks about spheres.
