Dithering vs Halftone
ディザリング / ハーフトーン（網点）
Dithering comes from Digital Image Techniques and Halftone from Print Expression. They are reached for with some of the same intent, which is where they get confused.
Dithering
Dithering suggests unavailable intermediate colors by spatially mixing pixels from a limited palette; ordered matrices or error diffusion make both tone and a distinctive granular surface.
Halftone
Halftone converts continuous tone into regularly spaced dots of changing size so it can be printed; from a distance they return to tone, while enlargement reveals the screen as material.
| Dithering | Halftone | |
|---|---|---|
| Era | 1960s– | 1880s– |
| Family | Digital Image Techniques | Print Expression |
| Kind | Technique | Technique |
| Cues | Two or more pixel colors mixed as checks or grain / High-frequency dots spreading around tonal boundaries / Apparent gradients made from a fixed palette / A pattern up close that becomes an intermediate color at normal distance | Large and small dots on one fixed pitch / Light and shade made by dot area / Rosettes from differently angled color screens / An image that changes between normal and magnified viewing |
| Best used for | Preserving photographic tone on low-color displays and e-paper · Using the grain of early computer images as deliberate digital material | Printing photographs in newspapers, magazines and packaging with limited inks · Using enlarged dots to make reproduction and print itself the subject |
| Type | Use bitmap or simple sans type that remains intact at low resolution. | Choose bold type or simple contours that survive conversion into dots. |
| Composition | Build broad tonal fields but control diffusion around contours and copy. | Place normal-scale image and enlarged screen together to exploit changes in viewing distance. |
| Material | Fix the palette first, then pass quantization error to neighboring pixels or place dots with a threshold matrix. | Set line frequency, dot shape, screen angle and ink color, then translate tone into dot area. |
| Caution | Adding monochrome noise is not dithering. The limited colors must approximate the source value. | Polka dots are not halftone. Dot size must carry continuous tone in relation to printing resolution. |