Calotype

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Example of a calotype: Photo "Schreiner in Lacock" from 1842/43, photographer: William Henry Fox Talbot
"The Ladder" - William Henry Fox Talbot, 1845

The calotype (from ancient Greek καλός kalós "beautiful" and τύπος týpos "picture [work]"; also talbotype ) is a method of photography invented around 1835 by the Englishman William Henry Fox Talbot (1800–1877) . It should not be confused with kallitypie , another early photographic process from the end of the 19th century.

history

As early as 1833 experiments were carried out with paper soaked in saline solution and then sensitized with silver nitrate solution after drying . When objects were placed on this paper, their structure emerged on the paper through exposure to light. Talbot called the drawings created in this way "photogenetic drawings". Based on these experiments, the idea of using a camera obscura in connection with this process arose . The argyrotype was created .

Talbot published his discovery until 1840 after being on the daguerreotype of Louis Daguerre had read. He improved his method so that it allowed similar exposure times. He patented the invention in 1841 under the term “calotype”. After the inventor, it is often referred to as a "talbotype". Talbot pursued patent infringers with legal proceedings, whereby he severely hampered the spread of his technology.

Procedure

The calotype is a negative process , i.e. H. In photography , a negative is created first. Because the calotype made it possible to produce any number of prints for the first time, this was a key technique . Talbot succeeded in doing this by waxing the initial image and thus obtaining a transparent negative that he was able to transfer to another light-sensitive paper and thus create a positive image. The contact print of a calotype can also be made on modern photo paper. Talbot iodized silver paper used for the recording: silver nitrate and potassium iodide were painted on a thin paper and gave a silver iodide compound . He placed pieces of paper coated with light-sensitive silver iodide in small cameras ( mouse traps ), which gave a negative image after exposure.

He had discovered that he could make a latent negative visible on heavily exposed paper if he treated it with a developer solution made from gallic acid and silver nitrate. The process was accelerated by heating. The negative was then fixed with potassium bromide or sodium thiosulfate . In order to make a correct-sided positive print from the paper negative, he soaked the paper in hot wax and thereby made it transparent. Now any number of positives could be produced with contact prints on further talbotype sheets.

In 1840 he was able to significantly shorten the exposure times by placing a paper treated with silver nitrate, gallic acid and acetyl acid after exposure in gallic acid until the latent image slowly appeared. The development of the image took only 30 seconds instead of the hours or minutes known up until then.

In the contemporary competitive process, the daguerreotype , however, photographic images were always unique . After this idea had become standard in most processes based on glass plates, George Eastman took it up and developed it into the basic technology of today's negative film .

Characteristic

Due to the use of paper as the basis of the negative, calotypes were always quite grainy. The paper structure of the negative was transferred to the positive when copying. This was a major disadvantage compared to the daguerreotype. However, the characteristics of the prints obtained were perceived by the proponents as "picturesque", especially since they appeared in changing, never exactly predictable colors. Indeed, artistically very impressive portraits and other results were achieved very early on by David Octavius ​​Hill and his partner Robert Adamson . Talbot was already using the advantages of the negative process to illustrate books with original prints.

See also

Other early photography methods:

Others:

literature

chronologically

Web links

Commons : Calotypes  - collection of images, videos, and audio files

Individual evidence

  1. ^ Wilhelm Gemoll : Greek-German school and hand dictionary . 9th edition. G. Freytag et al., Munich et al. 1965 (reviewed and expanded by Karl Vretska ).
  2. ↑ Klaus Beneke: Thomas Wedgwood [05/14/1771 Etruria (Stafforshire) - July 10, 1805 Eastbury (Dorset)] and John Frederick William Herschel (March 7, 1792 Slough near Windsor - May 11, 1871 Hawkhurst / Kent) and the history of the Photography, especially the fixation of images from 1800 to 1850. In: Klaus Beneke: Biographies and scientific résumés of colloid scientists, whose résumés are connected to 1996 (= contributions to the history of colloid sciences. Volume 8). R. Knof, Nehmten 1999, ISBN 3-934413-01-3 , pp. 60 ff. ( Uni-kiel.de PDF; 2.04 MB).