Diagrams of camera obscuras, c 1626-1630.
© Science Museum / Science & Society Picture Library
Illustrated plate taken from 'Rosa Ursina sive Sol', published by Christopher Scheiner in Bracciano, Rome, in 1626-1630. A camera obscura is a box or darkened room with a lens or hole through which an image of an external object is projected onto the opposite internal wall. Camera obscuras were known to the ancient Chinese and Greeks, and were used by Arab astronomers in the 10th century to observe the sun. During the Renaisance, artists used them to help them draw more accurately.