halftonedots

Halftonedots refers to the pattern of small dots used in halftone printing and imaging to simulate continuous-tone imagery with a limited palette, typically black and one or more ink colors. By varying dot size (amplitude modulation) or dot density (frequency modulation), halftone systems reproduce gradients and shades while using discrete ink deposits.

The technique originated in the 19th century as a means to reproduce photographs in newspapers and books. In conventional commercial printing, halftone screens are produced for each color separation (commonly CMYK), and screen angle and line frequency (lines per inch, lpi) are chosen to minimize moiré patterns and optimize tonal range for the substrate and press. Common dot shapes include round, elliptical, square and engineered forms designed for specific tonal response.

Two principal approaches are amplitude-modulated (AM) screening, which varies dot size on a regular grid, and frequency-modulated (FM) or stochastic screening, which uses uniformly sized dots distributed variably to build tone. Digital halftoning also encompasses ordered dithering and error-diffusion algorithms such as Floyd–Steinberg, used in displays and printers that cannot render continuous tones.

Practical concerns include dot gain (expansion of printed dots), registration, and viewing distance, all of which affect perceived tone and sharpness. Beyond technical use, halftone dots have cultural and artistic significance, adopted as an aesthetic in graphic design, illustration and pop art.