Dictionary tag: H

About hue and colour models

• Hue refers to the attribute of a colour that allows us to distinguish it from others on the colour spectrum, and it is a fundamental concept in colour theory.
• Different colour models define hue in slightly different ways and associate it with different families of terms, so it is best to associate it with a specific colour model to avoid confusion.
• For example:
  • The RGB colour model works in practice by asking three questions of any colour: how red is it (R), how green is it (G), and how blue is it (B).
  • The HSB color model defines a colour by its hue (H), measured in terms of an angle between 0° and 259° on a colour wheel, and then determines its saturation (S) and brightness (B).
• Examples of colour models include:
  • CMYK colour model
  • HSB colour model
  • RGB colour model
  • spectral colour model
• Examples of practical applications include digital design, stage lighting, and the mixing of oil or water-based paints, inks and dyes.

About the term hue here at lightcolourvision.org

• At lightcolourvision.org we use hue in relation to the colour models it belongs to.
• Colour models describe the attributes of colour in different ways.
• One of our favourites is the HSB colour model.
• The HSB colour model refers to hue alongside saturation and brightness.
• The HSB colour model is extensively used for digital design and can be used to describe any colour on a TV, computer or mobile phone.
• The CMYK colour model which is a subtractive colour model uses a different set of attributes because one of its main concerns is how coloured inks appear on paper.
• Cyan, magenta, yellow and black (K) can print almost any colour without referencing hue, saturation ord brightness.
• Because hue isn’t part of that vocabulary then in that context the term is best avoided.

About the human eye, light and RGB colour

• The human eye, and so human perception, is tuned to the range of wavelengths of light that make up the visible spectrum and so to the corresponding spectral colours between red and violet.
• The visible spectrum is the range of wavelengths of the electromagnetic spectrum that correspond with all the different colours we see in the world.
• To be exact, spectral colour is a colour corresponding to a single wavelength of visible light, but in everyday terms, spectral colours are usually composed of a narrow band of adjacent wavelengths.

• Because of the way the eye works, we can see all the colours of the visible spectrum when red, green and blue lights are combined at different intensities.
• The RGB colour model is designed to provide the exact stimuli to the light-sensitive cone cells in the retina to illicit perception of any predetermined colour.
• Mixing wavelengths of light corresponding with the RGB primaries enables the human eye to see almost any imaginable colour including colours such as magenta that are not part of the visible spectrum.