Photomechanical prints introduced commercially in the 1860s; commonly used in book illustration; can be difficult to distinguish from actual photographs.
 

Prints distinguished by patterns of dots or circular lines, or other indication of the screen interposed between the original image and the camera. Usually used to reproduce continuous tone originals, such as photographs, in books, newspapers, or other publications. First commercially available in the 1880s.
 

Prints produced from photographically prepared relief plates of engravings, drawings, and other works that consist of just two tones: the background and the image. The image may be composed of solid dark areas as well as lines, but it lacks tonal gradations. No screen markings.
 

Usually a lithographic process and referred to as offset lithographs. Introduced in 1906; by the 1970s, a widely used method for publishing text and illustrations.
 

Color photomechanical prints produced lithographically from photographs. The technique was developed in Switzerland in the 1880s by Photoglob Zurich and used until the early 1900s. The caption is often in gold lettering. The prints look deceptively like color photographs unless viewed with a magnifying glass.
 

Limited here to prints made by photoglyphy, photogalvanography, or other methods of obtaining an intaglio or relief printing plate from a photograph before the commercial viability of the line and halftone photomechanical print processes in the 1880s.
 

Prints that faithfully imitate photographs or other continuous tone originals. Hand-pulled prints from plates with an aquatint grain have an irregular pattern of dotting; prints from screened gravure plates have a regular pattern of dots but, unlike halftone prints, ink varies in density. Introduced in 1879.
 

Limited here to prints made directly from stones or zinc plates to which the image was photographically transferred. One such process was patented in the United States in 1858. For offset photolithography, search under OFFSET PHOTOMECHANICAL PRINTS.
 

Continuous tone photomechanical prints made by a carbon process introduced in the United States in 1870. Used through the 1890s, mainly for book illustrations. Difficult to distinguish from actual photographic prints, although slight surface relief may be visible.