"Sir Joshua Reynolds's camera obscura, c 1760-1780. "
© Science Museum / Science & Society Picture Library
"A camera obscura is a box or darkened room with a lens or hole for projecting the image of an external object onto the opposite inside wall. Camera obscuras were first used by Arab astronomers in the tenth century to observe the sun without looking directly at it. During the Renaissance artists used the camera obscura to project images directly onto the canvas to help them paint. This object belonged to the portrait- painter Sir Joshua Reynolds (1723-1792), first president of the Royal Academy of Arts."