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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Henry Fox Talbot | 2/3 | https://en.wikipedia.org/wiki/Henry_Fox_Talbot | reference | science, encyclopedia | 2026-05-05T04:07:21.239999+00:00 | kb-cron |
The "calotype", or "talbotype", was a "developing out" process, Talbot's improvement of his earlier photogenic drawing process by the use of a different silver salt (silver iodide instead of silver chloride) and a developing agent (gallic acid and silver nitrate) to bring out an invisibly slight "latent" image on the exposed paper. This reduced the required exposure time in the camera to only a minute or two for subjects in bright sunlight. The translucent calotype negative made it possible to produce as many positive prints as desired by simple contact printing, whereas the daguerreotype was an opaque direct positive that could be reproduced only by being copied with a camera. On the other hand, the calotype, despite waxing of the negative to make the image clearer, still was not pin-sharp like the metallic daguerreotype, because the paper fibres blurred the printed image. The simpler salted paper process was normally used when making prints from calotype negatives. Talbot announced his calotype process in 1841, and in August he licensed Henry Collen, the miniature painter, as the first professional calotypist. The most celebrated practitioners of the process were Hill & Adamson. Another notable calotypist was Levett Landon Boscawen Ibbetson. In 1842, Talbot received the Rumford Medal of the Royal Society for his photographic discoveries. In 1852, Talbot discovered that gelatine treated with potassium dichromate, a sensitiser introduced by Mungo Ponton in 1839, is made less soluble by exposure to light. This later provided the basis for the important carbon printing process and related technologies. Dichromated gelatine is still used for some laser holography. Talbot's later photographic work was concentrated on photomechanical reproduction methods. In addition to making the mass reproduction of photographic images more practical and much less expensive, rendering a photograph into ink on paper, known to be permanent on a scale of hundreds if not thousands of years, was clearly one sure way to avoid the problems with fading that had soon become apparent in early types of silver image paper prints. Talbot created the photoglyphic (or "photoglyptic") engraving process, later perfected by others as the photogravure process.
== Patenting controversy ==
Daguerre's work on his process had commenced at about the same time as Talbot's earliest work on his salted paper process. In 1839, Daguerre's agent applied for English and Scottish patents only a matter of days before France, having granted Daguerre a pension for it, declared his invention "free to the world." The United Kingdom, along with the British Empire, therefore became the only places where a licence was legally required to make and sell daguerreotypes. This exception is now usually regarded as both an expression of old national animosities, still smouldering just 24 years after Waterloo, and a reaction to Talbot's patent. Talbot never attempted to patent any part of his printed-out silver chloride "photogenic drawing" process and his calotype patent was not registered in Scotland. In February 1841, Talbot obtained an English patent for his developed-out calotype process. At first, he sold individual patent licences for £20 each; later, he lowered the fee for amateur use to £4. Professional photographers, however, had to pay up to £300 annually. In a business climate where many patent holders were attacked for enforcing their rights, and an academic world that viewed the patenting of new discoveries as a hindrance to scientific freedom and further progress, Talbot's behaviour was widely criticised. On the other hand, many scientists supported his patent and they gave expert evidence in later trials. In addition, the calotype method was free for scientific uses, an area that Talbot himself pioneered, such as photomicrography. One reason Talbot later gave for vigorously enforcing his rights was that he had spent, according to his own reckoning, about £5,000 on his various photographic endeavours over the years and wanted to at least recoup his expenses.
In 1844, Talbot helped set up an establishment in Russell Terrace (now Baker Street), Reading, for mass-producing salted paper prints from his calotype negatives. The Reading Establishment, as it was known, also offered services to the public, making prints from others' negatives, copying artwork and documents, and taking portraits at its studio. The enterprise was not a success. In 1851, the year of Daguerre's death, Frederick Scott Archer publicised the wet collodion process, which made it practical to use glass instead of paper as the support for making the camera negative. The lack of detail often criticised in prints made from calotype negatives was overcome, and sharp images, comparable in detail to daguerreotypes, could finally be provided by convenient paper prints. The collodion process soon replaced the calotype in commercial use, and by the end of the decade, the daguerreotype was virtually extinct as well. Asserting a very broad interpretation of his patent rights, Talbot declared that anyone using the collodion process would still need to get a calotype licence. In August 1852, The Times published an open letter by Lord Rosse, the president of the Royal Society, and Charles Lock Eastlake, the president of the Royal Academy, who called on Talbot to relieve the patent pressure that was perceived as stifling the development of photography. Talbot agreed to waive licensing fees for amateurs, but he continued to pursue professional portrait photographers, having filed several lawsuits. In 1854, Talbot applied for an extension of the 14-year patent. At that time, one of his lawsuits, against photographer Martin Laroche, was heard in court. The Talbot v. Laroche case proved to be pivotal. Laroche's side argued that the patent was invalid, as a similar process had been invented earlier by Joseph Reade, and that using the collodion process did not infringe the calotype patent in any case, because of significant differences between the two processes. In the verdict, the jury upheld the calotype patent but agreed that Laroche was not infringing upon it by using the collodion process. Disappointed by the outcome, Talbot chose not to extend his patent.
== 1844 calotype of Thomas Moore and the Talbot household ==