TALBOT, HENRY FOX Born 1800, died September 17, 1877. Retired from public life in 1834 to devote his whole time to scientific work. While sketching at Lake Como with Wollaston's camera lucida in October, 1833, he was struck with the idea of fixing images produced by that instrument, and six years of steady work at the problem followed. He was to some extent successful, and on January 31, 1839, he read before the Royal Society a paper on the process, which he called " Photogenic Drawing " ; this paper was after wards published in the Philosophical Maga zine. Prof. Faraday exhibited at the Royal Institution on January 25, 1839, a collection of Fox Talbot's "photogenic drawings," which were produced solely by the action of light, and at the same time described the process (which see, under the heading " Photogenic Drawing "). Daguerre was experimenting at the same time, and published his results in 1839, but the methods of the two men were different, that of Fox Talbot giving an image on paper, that of Daguerre produced an image upon a polished silver surface. The calotype process, often called the talbotype process, was patented by Fox Talbot on February 8, 1841, and was the subject of the third British photographic patent. Fox Talbot in 1843 patented the use of a hot solution of sodium hyposulphite for making the pictures of his process whiter and more per manent ; Sir John Herschel had suggested it in 1819, and again advocated its use in 1843. In
1843 Fox Talbot took his process to Paris, and in the following year (1844) began to publish his famous work " The Pencil of Nature." After the introduction of the Archer collodion process in 1851, he devised a modification of it by which shorter exposures were possible. A year later he invented a process of engraving upon steel plates by means of photography, and in 1854 he introduced albumen to give a gloss to the surface of paper on which photographs were printed. The calotype (or talbotype) process of making negatives upon paper was largely used by amateurs of the period, it being less costly and troublesome than the daguerreotype process, which was preferred by the profes sional portraitists.
Talbot was the first to describe the use of line and network screens for the purpose of breaking up the image into dots, and for this purpose he made use of crêpe, silk gauze, muslin, and lines ruled on glass. He did not realise, however, the idea of optical formation of the dot in the negative as now practised.