Creating a halftone image involves using varying-sized dots to achieve a screen-like effect. This technique adds depth and shading to flat areas, like those found in black-and-white photographs.
Printing an image using halftone must first be separated into its component colors. Each color is then printed individually using a specially engraved screen made of film or glass. This screen contains fine lines arranged in a grid pattern, with the width and spacing of these lines determining the resolution of the final image.
When ink is forced through the openings in the screen onto paper, the size of the printed dots depends on the width of these openings. If closely placed, they blend to form solid areas of color; if spaced further apart, they create a more distinct dot pattern resembling screens.
The versatility of the halftone allows it to be used for both black-and-white and color printing. It accurately reproduces continuous-tone images for prints or publications by utilizing varying dot sizes and spacing.
During printing, there may be an increase in dot size known as “dot gain.” This can result in darker and less detailed images.
Ultimately, halftone serves multiple purposes: faithfully reproducing continuous-tone images in prints or publications while creating realistic effects in black-and-white prints or adding visual appeal through illusionary continuous tones in color printing.