Camera obscura << ob SKYUR uh >> is a box used for sketching large objects or scenes. The term means dark chamber. The box contains a mirror set at a 45° angle. Mounted in the front end of the box is a double-convex lens like that in a photographic camera . Light from the object or scene is transmitted through the lens. The mirror reflects this light upward to a ground-glass screen on the top of the box. There, the light forms an image of the object or scene that can be sketched easily.
A darkened room may be used instead of a box for a camera obscura. In this case, the view from the outside world is transmitted through the lens and projected as an upside-down image on the far wall.
