page_title: Henry Fox Talbot
section_title: Photographic inventions
hierarchical_section_title: Henry Fox Talbot / Photographic inventions
caption_attribution_description: English: Window in the South Gallery of Lacock Abbey made from the oldest photographic negative in existence.
context_page_description: William Henry Fox Talbot FRS FRSE FRAS was an English scientist, inventor and photography pioneer who invented the salted paper and calotype processes, precursors to photographic processes of the later 19th and 20th centuries. His work, in the 1840s on photomechanical reproduction, led to the creation of the photoglyphic engraving process, the precursor to photogravure. He was the holder of a controversial patent that affected the early development of commercial photography in Britain. He was also a noted photographer who contributed to the development of photography as an artistic medium. He published The Pencil of Nature, which was illustrated with original salted paper prints from his calotype negatives, and made some important early photographs of Oxford, Paris, Reading, and York.
  A polymath, Talbot was elected to the Royal Society in 1831 for his work on the integral calculus, and researched in optics, chemistry, electricity and other subjects such as etymology and ancient history.
context_section_description: Talbot invented a process for creating reasonably light-fast and permanent photographs that was the first made available to the public; however, his was neither the first such process invented nor the first one publicly announced.
  Shortly after Louis Daguerre's invention of the daguerreotype was announced in early January 1839, without details, Talbot asserted priority of invention based on experiments he had begun in early 1834. At a meeting of the Royal Institution on 25 January 1839, Talbot exhibited several paper photographs he had made in 1835. Within a fortnight, he communicated the general nature of his process to the Royal Society, followed by more complete details a few weeks later. Daguerre did not publicly reveal any useful details until mid-August, although by the spring it had become clear that his process and Talbot's were very different.
  Talbot's early "salted paper" or "photogenic drawing" process used writing paper bathed in a weak solution of ordinary table salt (sodium chloride), dried, then brushed on one side with a strong solution of silver nitrate, which created a tenacious coating of very light-sensitive silver chloride that darkened where it was exposed to light. Whether used to create shadow image photograms by placing objects on it and setting it out in the sunlight, or to capture the dim images formed by a lens in a camera, it was a "printing out" process, meaning that the exposure had to continue until the desired degree of darkening had been produced. In the case of camera images, that could require an exposure of an hour or two if something more than a silhouette of objects against a bright sky was wanted. Earlier experimenters such as Thomas Wedgwood and Nicéphore Niépce had captured shadows and camera images with silver salts years before, but they could find no way to prevent their photographs from fatally darkening all over when exposed to daylight. Talbot devised several ways of chemically stabilizing his results, making them sufficiently insensitive to further exposure that direct sunlight could be used to print the negative image produced in the camera onto another sheet of salted paper, creating a positive.
caption: Latticed window at Lacock Abbey, August 1835. A positive from what may be the oldest existing camera negative.[5]
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