halotone

Halotone is a term used in printing and photography to describe an image reproduced from a grayscale original by means of halftone screening. In practice, halotone images are built from a matrix of tiny, fixed cells (dots) whose sizes or spacing vary with the tonal value of the original. Larger dots represent darker tones, smaller dots lighter tones. When printed with ink, these dot patterns trick the human eye into seeing a continuous gradient rather than discrete spots. The word is often used interchangeably with halftone, though some historical sources treat halotone as a specific subset, such as grayscale reproduction using a single screen.

The halftone process emerged in the late 19th century as a way to reproduce photographs in magazines and newspapers. Early experiments used line screens; later, photographic contact screens and rotary methods improved consistency and tonal range. The standard modern approach uses multiple color separations (CMYK), each with its own halftone screen, to reproduce color images.

In modern practice, halftone conversion can be done digitally; the output depends on screen frequency (lines per inch), screen ruling, dot shape (round, square, elliptical), and dot gain in printing. Dithering and stochastic screening offer alternatives to regular dot grids to reduce moiré and improve tonal fidelity.

Halotone or halftone remains common in newsprint, magazines, and art reproductions, though digital displays often prefer continuous-tone representations. The term halotone is less common in contemporary technical literature than halftone.