Early box-type camera obscura, early 19th century.

This early box-form camera obscura was probably made in England at the start of the 19th century. In operation, an image was formed with a lens that was reflected off a mirror onto a glas screen from beneath. The artist was thus able to lightly outline the projected picture using a soft pencil. Camera obscuras were known to the ancient Greeks, 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.