Tent camera obscura, 19th century.
© Science Museum / Science & Society Picture Library
Illustration of a man using a tent camera obscura in a rural setting, taken from E Atkinson's Natural Philosophy. 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. Camera obscuras were known to the ancient Chinese and Greeks, and used by Arab astronomers in the 10th century to observe the sun. During the Renaisance, artists used camera obscuras to help them draw more accurately.