TRADESMEN AS SCHOLARSThere were two principal drawbacks to the use of photography in the study of paintings at this time. First, the considerable amounts of light required for early exposures meant that many works �especially large ones �simply could not be illuminated sufficiently. Secondly, emulsions were selectively sensitive across the light spectrum, resulting in a translation from hue to tone that was either obscuring or misleading. Because yellow produced a dark tone it was often impossible to acquire any photographic image whatsoever of a heavily varnished painting.34 This characteristic only began to be overcome with the development of isochromatic emulsion in the 1890s, and panchromatic film in the 1920s. Nonetheless, Thor-Brger determined gathering of photographs of ostensible Vermeers marks a move in the direction of a practice taken for granted today and facilitated by the great photographic archives of works of art, such as the Witt Library in London, the Rijksbureau voor Kunsthistorische Documentatie in The Hague, and the Frick Art Reference Library in New York. The comparison of paintings as represented by their photographic simulacra is an entrenched component of modern connoisseurship.35 Although Thor-Brger set great store by photography in the positivist art history he was pioneering in his Gazette des Beaux-Arts study of Vermeer paintings, photomechanical reproduction for publication was not yet technically feasible. Between 1853 and 1854 Charles Blanc, editor of the Gazette des Beaux-Arts, had published a set of one hundred photographic reproductions after Rembrandt etchings under the title L櫯抲vre de Rembrandt reproduit par la photographie,36 yet not only was a combination of letterpress and photographic printing impossible, but a great deal of prejudice had to be overcome before photographs of works of art could be accepted. Critics such as Philippe Burty argued that interpretation by a skilled engraver or lithographer was preferable to the supposedly impersonal, undiscerning quality of a photographic reproduction, and indeed essential if the character of the original were to be conveyed adequately.37 Thor-Brger 1866 publication was therefore illustrated by other means: four woodcuts (plus the title design in the same medium) set with the letterpress, one lithograph, and three full page etchings interleaved within the letterpress signatures.38 Two of the woodcuts and two of the etchings reproduce paintings that were either then owned by Thor-Brger himself or, in one case, had recently been acquired from him.39 Thor-Brger published his catalogue raisonn of Vermeer works in the Gazette des Beaux-Arts in the fall following a major loan exhibition in Paris of old master paintings held between May and July 1866. He had been closely involved in the organization of the exhibition and took advantage of the opportunity to introduce the artist whose oeuvre he was so painstakingly reconstructing. Eleven paintings that Thor-Brger attributed to Vermeer were included. Of these no fewer than six belonged to him at the time, two of the others had been acquired through him by their then owners, and one had recently been attributed by him to Vermeer.40 Critical notices of the exhibition, and the impact of ThorBrger catalogue, ensured that Vermeer would never again lapse into obscurity. 157
