Daguerre

Daguerre was born in Cormeilles-en-Parisis, Val-d'Oise, France. He was apprenticed in architecture, theatre design, and panoramic painting to Pierre Prévost, the first French panorama painter. Exceedingly adept at his skill of theatrical illusion, he became a celebrated designer for the theatre, and later came to invent the diorama, which opened in Paris in July 1822.

In 1829, Daguerre partnered with Nicéphore Niépce, an inventor who had produced the world's first heliograph in 1822 and the first permanent camera photograph four years later. Niépce died suddenly in 1833, but Daguerre continued experimenting, and evolved the process which would subsequently be known as the daguerreotype. After efforts to interest private investors proved fruitless, Daguerre went public with his invention in 1839. At a joint meeting of the French Academy of Sciences and the Académie des Beaux Arts on 7 January of that year, the invention was announced and described in general terms, but all specific details were withheld. Under assurances of strict confidentiality, Daguerre explained and demonstrated the process only to the Academy's perpetual secretary François Arago, who proved to be an invaluable advocate. Members of the Academy and other select individuals were allowed to examine specimens at Daguerre's studio. The images were enthusiastically praised as nearly miraculous, and news of the daguerreotype quickly spread. Arrangements were made for Daguerre's rights to be acquired by the French Government in exchange for lifetime pensions for himself and Niépce's son Isidore; then, on 19 August 1839, the French Government presented the invention as a gift from France "free to the world", and complete working instructions were published.

In 1826, prior to his association with Daguerre, Niépce used a coating ofbitumen of Judea to make the first permanent camera photograph. The bitumen was hardened where it was exposed to light and the unhardened portion was then removed with a solvent. A camera exposure lasting for hours or days was required. Niépce and Daguerre later refined this process, but unacceptably long exposures were still needed.

After the death of Niépce in 1833, Daguerre concentrated his attention on the light-sensitive properties of silver salts, which had previously been demonstrated by Johann Heinrich Schultz and others. For the process which was eventually named thedaguerreotype, he exposed a thin silver-plated copper sheet to the vapor given off by iodine crystals, producing a coating of light-sensitive silver iodide on the surface. The plate was then exposed in the camera. Initially, this process, too, required a very long exposure to produce a distinct image, but Daguerre made the crucial discovery that an invisibly faint "latent" image created by a much shorter exposure could be chemically "developed" into a visible image. Upon seeing the image, the contents of which are unknown, Daguerre said, "I have seized the light – I have arrested its flight!"

The latent image on a daguerreotype plate was developed by subjecting it to the vapor given off by mercury heated to 75 °C. The resulting visible image was then "fixed" (made insensitive to further exposure to light) by removing the unaffected silver iodide with concentrated and heated salt water. Later, a solution of the more effective "hypo" (hyposulphite of soda, now known assodium thiosulfate) was used instead.

The resultant plate produced an exact reproduction of the scene. The image was laterally reversed—as images in mirrors are—unless a mirror or invertingprism was used during exposure to flip the image. To be seen optimally, the image had to be lit at a certain angle and viewed so that the smooth parts of its mirror-like surface, which represented the darkest parts of the image, reflected something dark or dimly lit. The surface was subject to tarnishing by prolonged exposure to the air and was so soft that it could be marred by the slightest friction, so a daguerreotype was almost always sealed under glass before being framed (as was commonly done in France) or mounted in a small folding case (as was normal in the UK and US).

Daguerreotypes were usually portraits; the rarer landscape views and other unusual subjects are now much sought-after by collectors and sell for much higher prices than ordinary portraits. At the time of its introduction, the process required exposures lasting ten minutes or more for brightly sunlit subjects, so portraiture was an impractical ordeal. Samuel Morse was astonished to learn that daguerreotypes of the streets of Paris did not show any people, horses or vehicles, until he realized that due to the long exposure times all moving objects became invisible. Within a few years, exposures had been reduced to as little as a few seconds by the use of additional sensitizing chemicals and "faster" lensessuch as Petzval's portrait lens, the first mathematically calculated lens.

The daguerreotype was the Polaroid film of its day: it produced a unique image which could only be duplicated by using a camera to photograph the original. Despite this drawback, millions of daguerreotypes were produced. The paper-based calotype process, introduced by Henry Fox Talbot in 1841, allowed the production of an unlimited number of copies by simple contact printing, but it had its own shortcomings—the grain of the paper was obtrusively visible in the image, and the extremely fine detail of which the daguerreotype was capable was not possible. The introduction of the wet collodion process in the early 1850s provided the basis for a negative-positive print-making process not subject to these limitations, although it, like the daguerreotype, was initially used to produce one-of-a-kind images—ambrotypes on glass and tintypes on black-lacquered iron sheets—rather than prints on paper. These new types of images were much less expensive than daguerreotypes, and they were easier to view. By 1860 few photographers were still using Daguerre's process.

The same small ornate cases commonly used to house daguerreotypes were also used for images produced by the later and very different ambrotype andtintype processes, and the images originally in them were sometimes later discarded so that they could be used to display photographic paper prints. It is now a very common error for any image in such a case to be described as "a daguerreotype". A true daguerreotype is always an image on a highly polished silver surface, usually under protective glass. If it is viewed while a brightly lit sheet of white paper is held so as to be seen reflected in its mirror-like metal surface, the daguerreotype image will appear as a relatively faint negative—its dark and light areas reversed—instead of a normal positive. Other types of photographic images are almost never on polished metal and do not exhibit this peculiar characteristic of appearing positive or negative depending on the lighting and reflections.

Competition with Talbot

Unbeknownst to either inventor, Daguerre's developmental work in the mid-1830s coincided with photographic experiments being conducted by Henry Fox Talbot in England. Talbot had succeeded in producing a "sensitive paper" impregnated with silver chloride and capturing small camera images on it in the summer of 1835, though he did not publicly reveal this until January 1839. Talbot was unaware that Daguerre's late partner Niépce had obtained similar small camera images on silver-chloride-coated paper nearly twenty years earlier. Niépce could find no way to keep them from darkening all over when exposed to light for viewing and had therefore turned away from silver salts to experiment with other substances such as bitumen. Talbot chemically stabilized his images to withstand subsequent inspection in daylight by treating them with a strong solution of common salt.

When the first reports of the French Academy of Sciences announcement of Daguerre's invention reached Talbot, with no details about the exact nature of the images or the process itself, he assumed that methods similar to his own must have been used, and promptly wrote an open letter to the Academy claiming priority of invention. Although it soon became apparent that Daguerre's process was very unlike his own, Talbot had been stimulated to resume his long-discontinued photographic experiments. The developed out daguerreotype process only required an exposure sufficient to create a very faint or completely invisible latent image which was then chemically developed to full visibility. Talbot's earlier "sensitive paper" (now known as "salted paper") process was aprinted out process that required prolonged exposure in the camera until the image was fully formed, but his later calotype (also known as talbotype) paper negative process, introduced in 1841, also used latent image development, greatly reducing the exposure needed, and making it competitive with the daguerreotype.

Daguerre's agent Miles Berry applied for a British patent just days before France declared the invention "free to the world". Great Britain was thereby uniquely denied France's free gift, and became the only country where the payment of license fees was required. This had the effect of inhibiting the spread of the process there, to the eventual advantage of competing processes which were subsequently introduced. Antoine Claudet was one of the few people legally licensed to make daguerreotypes in Britain. Daguerre's pension was relatively modest—barely enough to support a middle-class existence—and apparently this British "irregularity" was allowed to pass without adverse consequences or much comment outside of the UK.