halftoon

Halftoon is a reproduction technique that uses a pattern of small dots to simulate continuous tone in images. In a halftoon, each dot encodes brightness by its size, density, or both. When viewed from a normal distance, the human eye blends the dots into a smooth image, while up close the dot pattern remains visible.

The technique originated in the late 19th century as a method to reproduce photographs in mass print media. Halftone screens convert grayscale values into a grid of dots, enabling inexpensive printing of photographs alongside text. In color printing, separate halftone screens are used for cyan, magenta, yellow, and black, each printed at different angles to minimize moiré patterns and to create the impression of full color.

Technique and variations: In traditional halftoning, dot size or density varies with tone, a method known as amplitude modulation (AM) screening. Another approach, frequency modulation (FM) or stochastic screening, uses a fixed dot size with a variable spatial distribution to achieve tone. Dot shapes can be circular, squared, or other forms, and the screen frequency (lines per inch) and angles influence sharpness and texture. Digital halftoning can simulate halftoon effects using dithering or error-diffusion algorithms, producing patterns similar to conventional screens on modern displays and printers.

Applications and cultural impact: Halftoning remains common in newspapers, magazines, and packaging, as well as in art and design. The halftone aesthetic has been used deliberately to evoke a retro or comic-book look, notably in pop art and film. While modern printing increasingly relies on digital techniques, halftoon patterns continue to influence visual design and reproduction.

See also: Halftone, dithering, CMYK, screen printing.