Voigtlander daguerreotype camera, 1841.

This curiously-shaped camera for the daguerreotype proces was introduced by Peter Wilhelm Friedrich Voigtlander (1812-1878) in 1841. The focusing screen was positioned at the fattest part of the camera, and there was a magnifier in the shorter of the two cones to aid focusing. Once the picture was sharp, the photographer had to go into the darkroom and swap the focusing screen for a daguerreotype plate; to maintain sharpnes a special cradle ensured that the camera was replaced with the plate in precisely the same position. In the Daguerreotype proces, invented by Louis Daguerre (1789-1851) and made public in 1839, a picture made on a silver surface sensitized with iodine was developed by exposure to mercury vapour.