calotype

calotype

[kal-uh-tahyp]
noun
1.
an early negative-positive photographic process, patented by William Henry Talbot in 1841, in which a paper negative is produced and then used to make a positive contact print in sunlight.
2.
a print made by this process.
Also called Talbotype.


Origin:
1835–45; < Greek kalo- (combining form of kalós beautiful) + -type

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World English Dictionary
calotype (ˈkæləʊˌtaɪp)
 
n
1.  an early photographic process invented by W. H. Fox Talbot, in which the image was produced on paper treated with silver iodide and developed by sodium thiosulphite
2.  a photograph made by this process
 
[C19: from Greek kalos beautiful + -type]

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Encyclopedia Britannica
Encyclopedia

calotype

early photographic technique invented by William Henry Fox Talbot of Great Britain in the 1830s. In this technique, a sheet of paper coated with silver chloride was exposed to light in a camera obscura; those areas hit by light became dark in tone, yielding a negative image. The revolutionary aspect of the process lay in Talbot's discovery of a chemical (gallic acid) that could be used to "develop" the image on the paper-i.e., accelerate the silver chloride's chemical reaction to the light it had been exposed to. The developing process permitted much shorter exposure times in the camera, down from one hour to one minute.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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