Daguerreotype
John William Newland, Portrait of an Indian Army Officer, Calcutta, 1850s

Announced in Paris in 1839, the daguerreotype was the first publicly available photographic process. The daguerreotype image was created on a silvered metal plate exposed to iodine fumes, forming a light-sensitive surface of silver iodide. Development was achieved by exposing the plate to fumes of heated mercury and the image fixed in a salt solution. The daguerreotype produced an image of remarkable sharpness, but unlike competing processes, each daguerreotype was unique. This proved to be the major factor in its demise, compared to the negative-positive processes, from which unlimited copies could be made. J. W. Newland, the photographer of this portrait, had practised as a daguerreotypist in North and South America, the Pacific and Australia, before establishing a studio in Calcutta in about 1850. Although his studio remained successful throughout the 1850s, Newland himself died in 1857, one of the early victims of the Indian Mutiny.

Source : British Library