German photographer Revert Henry Klumb, meanwhile, settled in Rio in 1852, later moving to Petrópolis. By 1855, he had already created several stereoscopic views of the Imperial capital (stereoscopy uses paired photographs of the same scene which, seen through a binocular visor, give the illusion of three-dimensionality). This period saw important technological advances, such as glass negatives and albumen paper, allowing negatives to be copied; this allowed for the production of books of photography, with significant quantities of reproductions from a single negative.