The solar camera, or solar enlarger, is an ancestor of the darkroom enlarger, and was used in the mid-to-late 19th century to make photographic enlargements from negatives.
Other uses The name Solar was registered as the brand of an unrelated electrically illuminated darkroom enlarger marketed post-WW2 in the United States by Burke & James Inc., Chicago.
Description Early photographic materials were less light sensitive, and prints were made by simple superposition ("Contact prints"). The solar camera enlarger permitted photographers to make enlargements from glass negatives. However, exposures required for making such copies from negatives increase inversely with enlargement area. Photographers therefore employed the most powerful light source then available: the Sun. Solar cameras were at first freestanding, a design based on picture-taking cameras but with the relative position of negative and lens reversed so that sunlight shone through the glass plate to be projected onto photo-sensitive paper or an emulsion on other substrates (glass, fabric, leather etc.) inside the instrument. Mounted on a stand, they could be swivelled to continuously face the Sun, and were later built into the structure of a darkroom with an opening to the sky to admit light. The intensity of the light, and heat, they transmitted and concentrated through condensers can be gauged from reports of near loss of life when a fire started from a late version of the device, built in to a darkroom, was left unattended and still open to full sunlight. Jacob Wothly's huge version of the device required water troughs to keep it cool enough to use safely.
Inventors A number of photographers, inventors and photographic businesses contributed to the design development of the solar camera. An antecedent was the solar microscope of c.1740, employed in experiments with photosensitive silver nitrate by Thomas Wedgwood and Humphry Davy in making the first, but impermanent, photographic enlargements. Their discoveries were published in June 1802 by Davy in his An Account of a Method of Copying Paintings upon Glass, and of Making Profiles, by the Agency of Light upon Nitrate of Silver. Invented by T. Wedgwood, Esq. With Observations by H. Davy in the first issue of the Journals of the Royal Institution of Great Britain. John Towler, writing in 1864 is at pains to point out that; "The appendages to the solar camera and to the solar microscope are facsimiles of each other; but the solar microscope existed before photography had been elicited from chaos; the solar camera, therefore, is a mere imitation of its antecedent; the patentees of the latter instrument, then, can make no claim to originality of design; their only claim can be the application of the instrument to photography." Baltimore photographer and professor of drawing at the Government School of Design, David Acheson Woodward's 1857 solar enlarging camera was an evolution of the solar microscope, and was a large instrument operated out-of-doors that could produce life size prints from quarter plate and half plate negatives with an exposure of about forty-five minutes. During his visit to England to exhibit and market his device, the Liverpool Mercury reported that his pictures "were universally admired. One of the prints had been enlarged from 6+1⁄2 inches (17 cm) to about 3 feet [91 cm], and yet the greatest clearness and accuracy were preserved." His apparatus was made in two sizes: one with a 9 in (23 cm) condenser for half-plates that cost £21 (£2,845.61 or $US3,760.29 in 2020); the smaller had a 5 in (13 cm) condenser for quarter-plates costing £13. In 1860 the photo-microscopist Auguste-Adolphe Bertsch improved the Woodward design with a second condenser. Prominent London photographer the French-born Antoine Claudet was a user and active promoter of the solar camera, who lectured on the subject to the British Association in Oxford in June 1860, and in 1862 presented "On the means of following the small divisions of the scale regulating the distances and enlargement in the solar camera" at the British Association for the Advancement of Science in October. Earlier that year he exhibited a number of life-size portrait enlargements from carte de visite negatives at the 1862 World Fair, which were praised as 'magnificent' and 'without distortion', the reviewer noting that Claudet would have exhibited more but "for the continued absence of sunlight during the last few weeks."
In the 1860s and 1870s advances on Woodward's design were made. Jacob Wothly of Aachen improved Woodward's design with a reflector and condenser of one metre (39 inches) diameter and a focus of two meters (about 6½feet), attracting much attention, and presented it to the French Academy of Sciences, October 8, 1860, and at the Societe Francaise de Photographie in early November 1860, selling the design to Disderi, reportedly for 20,000 francs soon after, who was awarded a medal for his enlarged photographs at the 1862 London International Exhibition. Further adjustments to the original design included a clockwork heliostat, such as that invented by Léon Foucault in 1862 and built by his son-in-law, to rotate the mirror in synchronisation with the Sun's passage to concentrate its light on the condenser lens. Belgian photochemist and professional photographer Désiré van Monckhoven registered in August 1863 a patent for "an optical apparatus intended for enlarging by projection". It diverged from Woodward's design and had an appearance more like a modern horizontal enlarger and used a heliostat mirror instead of being pointed at the sun directly. It corrected for spherical aberration ("appareil solar dialytique") for sharper, more even light, for which he received a bronze medal at the Exposition Universelle (1867). After securing patents in England and France he went into manufacture. His apparatus was built into the darkroom wall, while J.F. Campbell's vertical design of the following year gathered light through an opening in the roof. Nadar used Alphonse Liebert's enlarger for his first enlargements around that time, a design which used a hand-operated drive to keep the condenser lens focussed on the sun directly; with no mirrors, exposure times were decreased. Louis Jules Duboscq's apparatus, like Quinet's, used electric light, and was shown to the Paris Photographic Society in 1861.
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