Early Photographic Processes
During the 1830s two different photographic processes were invented. The Daguerrotype became more popular at first. It was created by Louis Jacques Mande Daguerre, who created illusions for French theater, with help from Joseph Niepce, an inventor. Their process created images on copper plates coated with a mixture of photosensitive silver compounds and iodine. Dagurre realized he could significantly shorten the exposure time by using mercury vapor to intensify, or develop, the image after a relatively short exposure. This made the process more practical, but also dangerous to the photographer since mercury is poisonous. Also, no copies could be make of Daguerroptypes, making it virtually useless for purposes of reproduction.
A rival process was created in England by Fox Talbot, a scientist and mathematician. He created images on paper sensitized with alternate layers of salt and silver nitrate. Talbot also used development to bring out his image, resulting in exposure times of 30 seconds on a bright sunny day. Talbot's process produced negative images, where light areas appear as dark, and dark areas as light. By waxing these negatives to make them clear, and putting another sheet of photographic paper under them, Talbot could make an unlimited number of positive images. This process was called a Calotype.
The Daguerrotype produced a positive image with extremely fine detail and was initially more popular. The Industrial Revolution had helped create a growing middle class with money to spend, and an interest in new and better ways of doing things. Soon the area around Paris filled on weekends with families out to take portraits and landscapes. These early processes were so slow, however, that views of cities turned into ghost towns since anything moving became blurred or invisible. Portraits were ordeals for the sitter, who had sit rigidly still, often aided by armatures behind them.
Other photography processes followed quickly. Some were quite different than the previous two methods. One method, invented by French civil servant Hippoyte Bayard in 1839, used light as a bleach that lightened a piece of paper darkened with silver chloride and potassium iodide. Papers employing carbon and iron rather than silver were also used. Platinum chloride, though expensive, proved popular with serious or wealthy photographers because it rendered a fuller range of gray tones than any other process.
Because Calotype negatives were pieces of paper, prints made from them picked up the texture of the paper fibers, making the image less clear. As a result, many artists and inventors experimented with making negatives on pieces of glass. A popular method bound silver compounds in collodion, a derivative of gun cotton that became transparent and sticky when dissolved in alcohol. Negatives made using this process required a shorter exposure than many previous methods, but had to be developed while still wet. As a result, landscape photographers had to bring portable darkrooms around them. These wet collodion negatives were usually printed on a paper treated with albumen. This produced a paper with a smooth surface that could be used in large quantities and reproduced rich photographic detail.
Dry plates using silver bromide in a gelatin ground appeared in 1878. They proved popular because they were easier than wet plates, and were soon produced by companies throughout the United States and Europe. In 1883, manufacturers began putting this emulsion on celluloid, a transparent mixture of plant fibers and plastic. Because celluloid was durable and flexible, its use lead to the commercial development of negative film on long rolls that could be loaded into cameras. By 1895, such film came with a paper backing so that it could be loaded outside of a darkroom. It was also far more sensitive to light than early photographic processes. These developments made photography more accessible to the average person, and lead to the widespread popularity photography has today.
Roll film also proved important to the motion picture industry because it allowed a series of photographs to be recorded sequentially on the same strip of film.
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