A photomechanical printmaking process invented in 1879. A photographic image is transfered to a copper plate which is chemically etched. The plate is hand-inked for each print.Related link: "The Illustrated Book Study" is a collaborative effort undertaken by Cornell University Library's Department of Preservation and Conservation and Picture Elements, Inc, and the Library of Congress. On its Illustrated Book Study Resolution Samples pages, visitors can examine digital images of prints of several types (collotype, copper engraving, etching, halftone, lithograph, mezzotint, photogravure, steel engraving, and wood engraving) at each of several resolutions; dots per inch (DPI). see thumbnail to leftThe photogravure that can be downloaded at 200 and 930 dpi (2000 x 2000 pixel sample) is a photographic portrait by Elliott & Fry of John Ruskin (English, 1819-1900), writer and art critic. See dpi. Also see photography and positive.