Tonality is the overall light-and-dark register of a picture — the dominant value range that gives the image its prevailing brightness or darkness.
A picture can be high-key (predominantly light values, narrow range, often pale or chalky), low-key (predominantly dark values, often weighted with shadow), or middle-key (balanced across the range). Tonality is separate from palette in the strict sense — two pictures can share a palette but differ entirely in tonality if one is keyed bright and the other dark. Description often pairs tonality with temperature: a warm low-key picture, a cool high-key one. The term comes from music by analogy, where the key of a piece sets the underlying register that everything else plays against; the visual sense kept the same logic.
See also
- palette — the colours tonality keys
- contrast — the spread of values within the tonality
- monochrome — the case where tonality does almost all the work