If at this point in our discussion we revert once more to the realm of physical manifestations of light, dealt with in the preceding chapters, we do so because by studying them in the present context we shall gain further insight into the fact that one plane of nature provides illustrations of processes which on another plane remain more or less veiled. At the same time this will help us to learn more about the properties of levity-space. The optical phenomenon which we shall discuss in this sense is that of the so-called pin-hole camera. (The pin-hole camera effect is easily produced by a keyhole in a closed door which on one side faces a window and on the other leads to a comparatively dark room.)