Early box-type camera obscura.
© Science Museum / Science & Society Picture Library
A camera obscura is a box or darkened room with a lens or hole, through which the image of an external object is projected onto the opposite inside wall. This camera obscura is in the form of a box. Camera obscuras were known to the ancient Greeks and Chinese, and were used by Arab astronomers in the 10th century to observe the Sun. During the Renaisance period, artists used camera obscuras to help them to draw more accurately.