Development of a Halftone Screen

Description

Most of the book on the left is illustrated with a series of dull and lifeless halftone views of Nova Scotia, where the ill-fated Acadians immortalized by the poet Longfellow once lived. The frontispiece, however, is a rather charming tinted halftone reproduction of a painting featuring the maid Evangeline.

Investigators had long been in search of a reliable relief method for making a printing plate that could reproduce a full range of tonal values. The process had to be quick, economical, and capable of producing an image that could be printed along with the text type. The answer came with the development of the halftone screen, the principles of which were embodied decades earlier in the work of Fox Talbot. Process workers, as they came to be called, knew that a full range of tonal values on a printing plate could be rendered by breaking up an image into either regular or irregular patterns of lines, dots, or grain that – when viewed at a distance – coalesced into an accurate representation of the original. Small widely spaced dots could be used for highlight areas, while large, closely spaced dots simulated shadow areas.

It is impossible to ascribe the invention of an acceptable halftone screen to any one individual since many minds attacked the problem. The greatest success, however, came in the 1880s with the development of the cross-line screen by Frederick Ives and Max Levy of Philadelphia. Using their method, a halftone negative could be produced when their finely cross-hatched glass screen was interposed between a camera lens and a piece of film (holding the image to be reproduced). The negative was then exposed to a sensitized metal plate, which in turn was etched in nitric acid. The plate now held the image as a pattern of halftone dots, standing in relief and capable of being printed on a letterpress machine.

The book on the right is a rare copy of Frederic Ives’s account of his many inventions, and especially the halftone screen.

Keywords