Storer's 'Royal Delineator' camera obscura, 1778.

William Storer's 'Royal Delineator', an advanced form of camera obscura which was granted a British patent (No 1183). The superior design of the instrument uses a pair of rectilinear front lenses, a reflex mirror and third lens to give a bright overall image on its glas drawing screen. In operation, a picture was formed from the lenses 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 and Chinese and were used by Arab astronomers in the 10th century to observe the Sun.