Did You Know You Can't Print a Photograph?

At least not until it's converted to halftones, or patterns of dots which create the illusion of the original image. In order to convert a continuous-tone photo into a halftone, a printer must “lay” a screen over the print to break it into thousands of tiny dots. This screened image is then photographed to either negative film or positive paper, depending on the printing method to be used.

Photographs printed in one color are converted into a single halftone. Those that will be reproduced in two or four ink colors require separate halftones for each color.

Several factors determine the type of screen to be used. Newspapers, for example, require a fairly coarse screen (fewer dots per inch). That's because newsprint tends to be rather porous. With too fine a screen, dots would seep together, limiting detail and providing unacceptable reproduction quality. On the other hand, magazines and commercial printers can use much finer screens for greater photographic resolution and detail.

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