Daguerreotypes and calotypes

Louis Daguerre and Joseph Nicephore Niepce (who was Daguerre's partner, but died before their invention was completed) invented the first practical photographic method, which was named the daguerreotype, in 1836. Daguerre coated a copper plate with silver, then treated it with iodine vapor to make it sensitive to light. The image was developed by mercury vapor and fixed with a strong solution of ordinary salt (sodium chloride). Henry Fox Talbot perfected a different process, the calotype, in 1840. Both used cameras that were little different from Zahn's model, with a sensitized plate or sheet of paper placed in front of the viewing screen to record the image. Focusing was generally via sliding boxes. The daguerreotype pron.: /dr?ta?p/ (French: daguerreotype) was the first commercially successful photographic process, invented around 1837 by Louis-Jacques-Mande Daguerre. The physical daguerreotype itself is a direct positive made in the camera on a silvered copper plate. The raw material for plates was called Sheffield plate, plating by fusion or cold-rolled cladding and was a standard hardware item produced by heating and rolling silver foil in contact with a copper support.[2] The surface of a daguerreotype is like a mirror, with the image made directly on the silvered surface; it is very fragile and can be rubbed off with a finger, and the finished plate has to be angled so as to reflect some dark surface in order to view the image properly. Depending on the angle viewed and the color of the surface reflected into it, the image can change from a positive to a negative. The cases provided to house daguerreotypes have a cover lined with velvet or plush to provide a dark surface that reflects into the plate for viewing.[3] The daguerreotype was the dominant photographic process until the 1850s when other processes such as the col

odion process and tintype replaced it. At the time the process was introduced, daguerreotyping a brightly sunlit subject typically required about ten minutes of exposure in the camera, so the earliest daguerreotypes were of still lifes and landscapes. The oldest well-documented daguerreotype featuring human subjects is Daguerre's own 1838 view of the Boulevard du Temple, a busy street in Paris. The street appears deserted because the traffic (which would have been horse-drawn carriages) was moving and left no impression; but a man having his shoes shined and the bootblack servicing him are visible because they stayed in position long enough for their images to be recorded. Calotype or talbotype is an early photographic process introduced in 1841 by William Henry Fox Talbot,[1] using paper[2] coated with silver iodide. The term calotype comes from the Greek ? (kalos), "beautiful", and ? (tupos), "impression". Talbot made his first successful camera photographs in 1835 using paper sensitized with silver chloride, which darkened in proportion to its exposure to light. This early "photogenic drawing" process was a printing-out process, i.e., the paper had to be exposed in the camera until the image was fully visible. A very long exposure—typically an hour or more—was required to produce an acceptable negative. In the fall of 1840, Talbot worked out a very different developing-out process in which only an extremely faint or completely invisible latent image had to be produced in the camera, which could be done in a minute or two if the subject was in bright sunlight. The paper, shielded from further exposure to daylight, was then removed from the camera and the latent image was chemically developed into a fully visible image. This major improvement was introduced to the public as the "calotype" or "talbotype" process in 1841.