The daguerreotype was the Polaroid film of its day: it produced a unique image which could only be duplicated by using a camera to photograph the original. Despite this drawback, millions of daguerreotypes were produced. The paper-based calotype process, introduced by Henry Fox Talbot in 1841, allowed the production of an unlimited number of copies by simple contact printing, but it had its own shortcomings—the grain of the paper was obtrusively visible in the image, and the extremely fine detail of which the daguerreotype was capable was not possible. The introduction of the wet collodion process in the early 1850s provided the basis for a negative-positive print-making process not subject to these limitations, although it, like the daguerreotype, was initially used to produce one-of-a-kind images—ambrotypes on glass and tintypes on black-lacquered iron sheets—rather than prints on paper. These new types of images were much less expensive than daguerreotypes, and they were easier to view. By 1860 few photographers were still using Daguerre's process.