About Calotypes

Fig. VII.3.   Leavitt Hunt and Nathan F. Baker.
Grand Colonnade of Karnak, Egypt.  (Dec. 1851 or Jan. 1852)
Salt print from calotype negative.  22.9 cm. x 18.4 cm.
Library of Congress, Prints & Photographs Division.
Definition of calotype: Calotype or talbotype is an early photographic process introduced in 1841 by William Henry Fox Talbot. Talbot made his first successful camera photographs in 1835 using paper sensitized with silver chloride, which darkened in proportion to its exposure to light. This early "photogenic drawing" process was a printing-out process, i.e., the paper had to be exposed in the camera until the image was fully visible. A very long exposure—typically an hour or more—was required to produce an acceptable negative. In the fall of 1840, Talbot worked out a very different developing-out process in which only an extremely faint or completely invisible latent image had to be produced in the camera, which could be done in a minute or two if the subject was in bright sunlight. The paper, shielded from further exposure to daylight, was then removed from the camera and the latent image was chemically developed into a fully visible image. This major improvement was introduced to the public as the "calotype" or "talbotype" process in 1841.