In 1854 Viennese photographer resident in London Paul Pretsch patented a process called "photo-galvanography" for the printed reproduction of photographs. The first print that Pretsch issued was called "Scene in Gaeta after the Explosion." It was "the first relief half-tone and the first commercial use of half-tone" (Printing and the Mind of Man. Catalogue of the Exhibitions Held at the British Museum and at Earls Court, London  No. 629).
In November 1856 Pretsch issued through his Patent-Photo-Galvano-Graphic Company the first fascicule of a book entitled in an oddly circular manner Photographic Art Treasures, or, Nature and Art Illustrated by Art and Nature. This fascicule, which also immodestly characterized itself as "A New Era in Art" on its printed cover, was the first part of the first book of printed reproductions of photographs, as distinct from books illustrated with pasted-in original photographs. A total of five fascicules were published between November 1856 and July 1857, each with 4 "photo-galvano-graphic" plates.
Pretsch's photo-galvanographic process began with a photographically exposed dichromated-gelatine mould which was made to reticulate, from which he produced a copper intaglio plate by galvanoplasty. His halftone method was not entirely original. Others had developed methods of engraving from photographs. As early as the 1830s William Fox Talbot had patented a method of using "photographic screens or veils" in connection with a photographic intaglio process.
"However, Pretsch's system achieved one thing that no others had previously managed— the inclusion of half-tones— the greys which make the photographic image unique. At the time, the half-tone dot screen had not yet been invented and all engravings from photographs such as those used in the Illustrated London News from Fenton's Crimea portraits, were hand-drawn impressions of the original photograph. Even the more advanced process which Pretsch was now attempting to market did not completely dispose of the need for long and careful hand-retouching on the part of the engraver and it took an average of six weeks hard work to prepare just one plate. After all that work, only about five hundred prints could be made before the image started to break up. As with all such processes, the first prints were of a far superior quality to the last— so a sliding scale of charges was evolved, the price depending on the state of the plate at the time the print was made. . . .
"Pretsch was no photographer, however, and he left it to others to provide the pictures for his patent process. Roger Fenton took up his appointment as manager of the Photographic Department and chief photographer, in August 1857. . . .In the short time Fenton had been employed at Holloway Place, the company's head office in Holloway Road, he had not had time to acquire prints by other photographers and so that the first publication of four prints [in the first fascicule of Photographic Art Treasures] was entirely his own work. . . ." (Hannaway, Roger Fenton of Crimble Hall  65-67).
Paul William Morgan, "Paul Pretsch, Photogalvanography and Photographic Art Treasures," accessed 01-12-2015).
Goldschmidt & Naef, The Truthful Lens (1980) No. 131.