Copy assembly consists of bringing all original work (text, pictures, and illustrations) together and preparing photographic images. The photographic images are in the form of either positive or negative films and are used for photomechanical image carrier preparation. Copy must be set up correctly to ensure the finished image carrier will produce a high quality print. Assembled copy that is ready for the photographic process is called a flat. When copy of various sizes and shapes is assembled for transfer to film the process is called image assembly or stripping. The printing industry depends heavily on the use of highly specialized photographic equipment, methods, and materials to produce high quality printed material. Process photography refers to the photographic techniques used in graphic arts. Prior to the invention of electronic page making systems, virtually all printing processes employed photomechanical methods of making image carriers.

 

Two important types of photography used in the preparation of image carriers are line and halftone photography. Neither of these processes can be used to print a true continuous-tone photograph (i.e., a photograph with intermediate or graduated tones) though halftone can achieve the illusion of continuous tones. Letterpress, lithography, screen printingand some gravure methods involve both these types of photography.

Line photography is used to produce high contrast images on film. Image areas on the film are solid black; little or no illusion of intermediate tones can be achieved with this method.

 

As noted above, by using halftone photography the illusion of intermediate tones can be achieved for letterpress, lithography, lateral dot gravure, and screen printing. In halftone photography, continuous-tone images are broken down into high-contrast dots of equal density but varying sizes and shapes. (Depending upon the type and quality of printing being done, the density of dots varies from 24 to 120 per centimeter). If, for example, very small dots are used in one area of an image, that area appears to be lighter than those areas of the image where larger dots are used. This occurs because more of the lighter color substrate remains visible in the areas where the very small dots are used.

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