camera obscura

A pinhole camera has no lens but can nevertheless produce a sharp inverted image because only one ray from a particular point can enter the tiny pinhole aperture, and so no blurring takes place. However, the very low amount of light entering the camera also means that the film at the back must be exposed for a long time before a photographic image is produced; the camera is therefore only suitable for photographing stationary objects.

Darkened box with a tiny hole for projecting the inverted image of the scene outside on to a screen inside. For its development as a device for producing photographs, see photography.

The camera obscura was invented by the Greek philosopher Aristotle in the 4th century BC. In its simplest form it was a dark room with a small hole through one wall. Light rays, travelling in straight lines, could pass through the hole and transmit the inverted image of the outside scene. The camera obscura was originally used to help artists to draw. Landscapes, for example, could be projected, traced, and then used as a perfect base drawing for a later painting.