Calotype

The talbotype (also calotype from Ancient Greek καλός kalós "beautiful" and τύπος typos " image [ factory ] ") is a 1835 by the Englishman William Henry Fox Talbot ( 1800-1877 ) invented recording process of photography.

History

Already in 1833, experiments were carried out with a soaked by saline and after drying sensitized with silver nitrate solution paper. You put on this paper objects, they were characterized by light in their structure on the paper. The sign-offs generated so called Talbot " Fotogenische drawings " ( "Photo Genetic Drawings" ). Based on these experiments arose the idea to use a camera obscura in connection with this process. It was the Argyrotypie.

Talbot published his discovery until 1840, after he had read about the Daguerreotype of Louis Daguerre. He improved his process so that it allowed similar exposure times. The term " calotype " he made the invention patented in 1841. According to the inventors, it is also often referred to as " Calotype ". Talbot pursued infringers with court proceedings, thereby greatly handicapped the spread of its technology.

Method

In the calotype is a negative process, that is, in photography initially produces a negative. Because the calotype, the opportunity arose for the first time to create any number of deductions, this was a key technique. The contact sheet of calotype process can also be done on a modern photo paper. Used for recording Talbot Jodsilberpapier: silver nitrate and potassium iodide were spread on a thin paper and there were a Silberiodidverbindung. He put in small cameras (Mouse Traps [= mousetraps ] ) with light-sensitive silver iodide coated paper pieces that show a negative figure after exposure.

He had discovered that he could make a latent negative on a heavily exposed paper visible when he treated it with a developer solution of gallic acid and silver nitrate. The process was accelerated by heating. With potassium or sodium thiosulfate, the negative was then fixed. To create a page of the paper negative real positive trigger, he soaked the paper in hot wax and made it becomes transparent. Now could be produced with contact sheets on other talbotype leaves as many positives.

In the contemporary competitive process, the daguerreotype, were photographic images, however, always unique. Once this idea had become standard in most glass-based plates procedures, including George Eastman handle on it and developed the basic technology of today's negative films.

Characteristics

Due to the use of paper as the basis of the negative Talbotypes were always quite grainy. The paper structure of the negative was also transferred when copying to the positive. This was a crucial drawback compared to the daguerreotype. However, the characteristics of the obtained prints of the supporters as was " picturesque " felt, especially since they also appeared in changing, never entirely predictable colors. In fact, by David Octavius ​​Hill and Robert Adamson his partner were very early artistically impressive portraits and other results. The advantages of the negative procedure already used Talbot for the illustration of books with original prints.