A camera obscura made, or perhaps simply owned, by Canaletto, as revealed by the inscription "A. CANAL" on the protective cover. Also known as a "pinhole camera," this is a real scientific instrument that has been documented since the Middle Ages and was used from the mid-16th century as an artist’s tool. In the 18th century, Canaletto made it one of the main tools used by landscape painters. The camera obscura comprises a wooden box fitted with a lens, a reflective mirror and a projection surface made from polished glass. The lens
consists of a cardboard tube with a converging lens on the end (diameter: 33 mm; focal distance: 400 mm). Inside the box, a mirror placed at a 45° angle receives the upturned image from the lens and reflects it, the right way up, onto the polished glass. On top of the glass (200 x 200 mm), the artist would lay a sheet of thin paper, either waxed or semi-transparent, on which he could record the images reflected by the mirror. At the start of the 19th century, the device was modified to make it a real photographic camera.
These sheets were inserted after the camera obscura. The first illustrates other parts of the Grand Canal and the second, which also relates to Venice, offers a glimpse of Murano.