The Daguerreian Annual 1997

The daguerreotype was the first publicly announced photographic process. It was developed by Louis Daguerre and Joseph Nicéphore Niépce. Niepce had produced the first photographic image in the camera obscura using asphaltum on a copper plate sensitised with lavender oil that required very long exposures. The image is formed by the amalgam, or alloy, of mercury and silver. Mercury vapor from a pool of heated mercury is used to develop the plate that consists of a copper plate with a thin coating of silver rolled in contact that has previously been sensitised to light with iodine vapour so as to form silver iodide crystals on the silver surface of the plate. Exposure times were later reduced by using bromine to form silver bromide crystals, and by replacing the Chevalier lenses with much larger, faster lenses designed by Joseph Petzval. The image is formed on the surface of the silver plate that looks like a mirror. It can easily be rubbed off with the fingers and will oxidize in the air, so from the outset daguerreotypes were mounted in sealed cases or frames with a glass cover. When viewing the daguerreotype, a dark surface is reflected into the mirrored silver surface, and the reproduction of detail in sharp photographs is very good, partly because of the perfectly flat surface. Although daguerreotypes are unique images, they could be copied by redaguerreotyping the original Artists and inventors, since the late Renaissance, had been looking for a mechanical method of capturing visual scenes.Previously, using the camera obscura, artists would manually trace what they saw. Previous discoveries of photosensitive methods and substances-including silver nitrate by Albertus Magnus in the 13th century, a silver and chalk mixture by Johann Heinrich Schulze in 1724, and Nichole Niépce's bitumen-based heliography contributed to development of the daguerreotype.