About additive and subtractive colour models
There are two main types of colour models, additive and subtractive.
Additive Colour Models
- Additive colour models are used when blending light to produce colour.
- The primary colours for most additive models are red, green, and blue (RGB).
- When combined at full intensity, they produce white light.
- The additive RGB model (and HSB colour model) is central to display technologies such as computer screens, TVs and phone screens.
- The additive spectral colour model is particularly useful for developing an understanding of the relationship between wavelengths of light within the visible spectrum and corresponding colours.
- Additive models are based on the way human eyes perceive colour, with each colour being produced by a combination of different wavelengths. In contrast, a subtractive model is based on the way pigments reflect light.
Subtractive Colour Models
- Subtractive colour models are used when working with pigments, inks and dyes.
- The primary colours for most subtractive colour models are cyan, magenta, and yellow (CMY).
- When combined cyan, magenta, and yellow produce black.
- The subtractive CMY colour model and CMYK colour model are central to printing technologies.
- In practice, the CMY colours often can’t produce a perfect black when mixed due to impurities in the pigments or inks, so a fourth ‘Key’ component (represented as K) is often used in printing to produce a true black.