Camera obscura, 1754.
© National Media Museum / Science & Society Picture Library
From the Dictionary of Arts and Sciences. 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.