The birth of photography cannot be attributed to a single person. Many individuals were involved in developing early photography yet the people who were exclusively involved in the development of the first two complete processes are considered the pioneers of photographic practice.

Daguerreotype

The first published and patented photographic process, takes its name after its inventor, the painter Louis Jacques Mandé Daguerre (1787-1851); its beginnings, however, must be credited to the French inventor Nicéphore Niépce (1765-1833), who in 1816 created the first negative image which he called the heliograph (sun-writing). The heliograph was successful in imprinting a trace when exposed to sunlight but the trace was not permanent. Niépce and Daguerre collaborated to investigate a way to create a positive and fixed image. Daguerre took over the experimentation after Niépce's death and, in 1839, published his results which he named Daguerreotypie.

The Daguerreotype was initially a two-part process of sensitisation and development. The surface was a polished silver-plated sheet of copper with photosensitive silver iodide on its surface. When the plate was exposed to light it formed a latent image; an image which exists but is not visible before development – all contemporary film and paper exposures are latent images before development. The plate was fumigated with mercury to make the image visible and fixed in a salt bath which partly insensitised unexposed silver. The end result is a mirror surface which, when it reflects a dark field, appears positive.

The daguerreotype has absolutely no grain and is, to this day, the sharpest, most detailed photographic print achievable. It is, however, a one-off photograph because it is not transparent to allow light through to create another copy. This was problematic for a culture which required mechanical reproducibility. The daguerreotype initially required very long exposures which made it totally impractical for portraiture until later refinements were made.

Photogenic Drawing

The English polymath William Henry Fox Talbot (1800-1877) had been experimenting with the effects of light on chemically treated surfaces since 1833 and independently of Daguerre. He was inspired to do so after failing to manually sketch the scenery of Lake Como.

Talbot envisioned a machine that would automatically, with the aid of physics and chemistry, record what he could not achieve with hand alone. This experimentation, using practices already in his arsenal, resulted in the Photogenic Drawing.

Talbot's process used photosensitive silver chloride, which is insoluble in water, on paper which was then contact printed in sun light. The areas of the paper not obscured by the opacity of the object darkened to form a negative. When the print was washed in salt and potassium iodide it left a semi-permanently fixed image. The Photogenic Drawing is the basis of the Salt print. In 1835, Talbot observed the potential of obtaining a positive from the original print.

The Calotype

In 1841, Talbot improved the Photogenic Drawing process. He realised that the image exists before it is visible (latent image), which shortens the exposure time and relies on an after-treatment with gallic acid and silver nitrate (development). Hypo was used as fixer. The calotype was a negative image. The original salt printing method with the addition of hypo was used to contact print a positive.

The calotype negative and salt-print positive were the most practical of the two pioneering processes. They were cheaper to make and most importantly could produce multiple copies. The pioneering Scottish photographers Hill & Adamson  used these methods very effectively and almost exclusively. They are also the first photographers to achieve artistic success with the process. The National Galleries of Scotland hold the largest collection of their work in the world. The Collection also includes work by other salt print photographers such as Archibald Burns and Thomas Keith.

Improvements

Meanwhile, the daguerreotype, which is the most detailed of the two processes, underwent an accelerating alteration. This was done by adding a bromine coating stage to the process and a gilding/gold-toning to the after-treatment which intensified the light areas of the plate. The alterations allowed the process to be used for portraiture; the photographic practice which sustained the Victorian love-affair with photography.

Conclusion

The driving forces for the creation of photography were the need to create a permanently fixed image and one that can reproduce multiple copies. This resulted in the invention of the Daguerreotype and the Calotype. Both were used almost exclusively for two decades and are still practiced today, either in their original form or a close derivation. Crucially, these experimentations on the chemical properties of photosensitive compounds paved the way for all analogue photography.

Both processes prompted the creation of the wet plate collodion technique which furthered the efficiency and use of photography. This was a much speedier and cheaper technique which can produce both a unique tin positive –ferrotype/tintype (like the Daguerreotype) and a glass plate collodion negative which can be endlessly reproduced (like the Calotype) but which can also be viewed as a unique positive when underexposed and backed with black velvet so it reflects light against the dark background – ambrotype . 

The calotype and salt print were the forefathers of contemporary black and white photography, at least conceptually. Together, these processes gave birth to analogue photography as we now understand and practice it. The early 1800s' investigations led to the birth of a medium that, although radically different in its current manifestation, is ubiquitous in our culture and whose use does not appear to wane.