ABSTRACT
The trades of philosophical instrument maker and manufacturing optician were well established in 1800. Instruments such as sextants and theodolites or levels incorporated a telescope as well. In 1839 the Daguerreotype and Calotype were introduced as the first photographic processes. In the published description of his process, Louis Daguerre carefully prescribed the lens for his camera thus: ‘the object glass should be an achromatic and periscopical one, its diameter ought to be eighty-one millimetres, and its focus thirty-eight centimetres. Richard Beard opened his first photographic studio at the Royal Polytechnic Institution, Regent Street on 23 March 1841. Photographic achromatization was satisfactory for the later orthochromatic materials too but correction had to revert to the visual type for panchromatic materials. Lenses with photographic achromatization appeared in several variations, using experience of telescope objectives. Lenses of large aperture were needed by portrait photographers to reduce exposures.
