If light is allowed to enter a darkened room through a tiny hole in a wall or door, the scenery outside will be projected onto the opposite wall. This phenomenon, known as pinhole projection, is one of the basic principles behind photography. The image created by pinhole projection is a reverse image, both upside-down, and left and right reversed. A pinhole camera can be easily created by opening a pinhole in a box that otherwise lets in no light. The hole should be covered with tape, and a sheet of photo printing paper placed inside, opposite the hole, without exposing it to light. The box should then be pointed in the direction of the scenery to be filmed, and the tape removed from the pinhole to allow light in for a few seconds. If the printing paper is placed in developing solution, the scenery will gradually appear in reverse on the printing paper. Present-day cameras work on the same principle, but with a lens, aperture ring and shutter affixed to the pinhole to adjust focus and light, and film or CCD to replace the wall or printing paper.