The British inventor Fox Talbot produced his first successful photographic images in 1834, without a camera, by placing objects onto paper brushed with light-sensitive silver chloride, which he then exposed to sunlight. By 1840, Talbot had succeeded in producing photogenic drawings in a camera, with short exposures yielding an invisible or ‘latent’ image that could be developed to produce a usable negative. This made his process a practical tool for subjects such as portraiture and was patented as the calotype in 1841. The calotype shown here is from 1842. Talbot’s negative-positive process formed the basis of almost all photography on paper up to the digital age.
the combination of operations by which a positive image is obtained from a negative. The positive process consists of exposing the material, such as photographic paper, a positive film, or diapositive plate, and processing it with photographic chemicals. The emulsions used in this process, whether for motion-picture or still photography, are less sensitive to light and more contrasty than those of negatives; moreover, the emulsions of black-and-white materials usually have not been color-sensitized.