13. Reflex Camera Obscura with Large Aperture Lenses, 1778

Signed: 'By the KING'S PATENT, THE ROYAL-DELINEATOR; To be had of no one but W. Storer', The address is added in ink; 'N 14 Lisle Street Leicesters Fields' [now Leicester Square].

The image cast on the ground glass screen was bright for indoor use by candlelight because of the much improved lens system consisting of large aperture rectangular lenses. A third lens increased the illumination at the corners and edges of the screen in the same way as a Fresnel lens makes a bright viewfinder image in a modern reflex camera. On the other hand, the large lens aperture permits only a small depth of field, hence rackwork was added to facilitate focusing. There is a black-painted, tin-plate, folding eye shade.

Length 310 mm, width 165 mm, height 198 mm.
Inventory no. 62,524.