About bands of colour, spectral and non-spectral colours
Bands of colour
- Bands of colour are composed of a continuous range of wavelengths, so for example:
- A continuous range of wavelengths between 750 – 620 nanometres (nm) typically appear red to an observer.
- Wavelengths between 590 – 570 nm will typically appear yellow.
- A continuous range of wavelengths between 450 – 380 nm will typically appear violet.
- A spectral colour is a colour that is evoked by a single wavelength of light (or narrow band of wavelengths) within the visible spectrum.
- Spectral colours are the colours red to violet.
- Diagrams of the spectral colour model are linear and may show colours selected:
- Using equal and incremental steps in wavelength.
- According to equal and incremental steps in the appearance of colours.
- Non-spectral colours are produced by additive mixtures of wavelengths of light.
- Examples of non-spectral colours produced by two spectral colours are:
- Purple – produced by mixing wavelengths corresponding with red and violet. Red (740nm) and violet (400nm) are at the extreme limits of the visible spectrum.
- Magenta – produced by mixing red (660nm) and blue (490nm).
- Mauve – produced by mixing orange (600nm) and blue (450nm).
- Examples of non-spectral colours produced by three spectral colours are:
- So all achromatic colours are non-spectral colours.
- Whilst both spectral and non-spectral colours are produced by mixing a combination of colours corresponding with different wavelengths of light:
- The RGB colour model produces a full gamut of colours by mixing red, green and blue primary colours in different proportions.
- The CMY colour model produces a full gamut of colours by mixing cyan, magenta and yellow primary colours in different proportions.