Brightness: HSB colour model

This entry deals with the term brightness as used in the HSB colour model, where H = hue, S = saturation and B = brightness.

Brightness (colour brightness) refers to the difference between the way a colour appears to an observer in well-lit conditions compared with its subdued appearance when in shadow or when poorly illuminated.

About brightness
  • The term brightness is best understood when associated with a specific colour model.
  • Examples of colour models include:
  • The HSB colour model uses the term brightness alongside hue and saturation.
  • Some colour models don’t use the term brightness at all.
  • When we change from one colour model to another, it’s best to change our terminology as well.
About colour models

Colour models are the how-to part of colour theory. Together they establish terms and definitions, rules or conventions and a system of notation for encoding colours and their relationships with one another.

A colour model is a way to:

  • Make sense of colour in relation to human vision, to the world around us and to different media and technologies.
  • Understand the relationship of colours to one another.
  • Understand how to mix a particular colour from other colours to produce predictable results.
  • Specify colours using names, codes, notation, equations etc.
  • Organise and use colours for different purposes.
  • Use colours in predictable and repeatable ways.
  • Work out systems and rules for mixing and using different media (light, pigments, inks).
  • Create colour palettes, gamuts and colour guides.
Colour theory
  • When an observer asks themselves about the colour of something, they will often unconsciously think in terms of a particular colour theory associated with:
    • Spectral colours with names associated with atmospheric rainbows
    • Pigments, where powders are mixed with water, oil or acrylic to produce different colours
    • Objects and surfaces which transmit, reflect and absorb wavelengths of light in different proportions
  • A broader vocabulary of names can be used to describe colours such as dark red, vermilion, golden yellow, lemon yellow, pale yellow, greenish-yellow, chartreuse, leaf green or light green.
  • A colour model derived from a theory of colour allows for a more exact and reproducible approach to colour.
HSB colour model

The HSB colour model is an additive colour model used to mix light. Subtractive colour models are used to mix pigments and inks.

  • HSB is an alternative to using the RGB colour model in so far as both deal with mixing red, green and blue light to produce other colours.
  • HSB is popular because it provides an intuitive way to select and adjust colours when using applications such as Adobe Creative Cloud for design, photography or web development.
  • The HSB colour model can be used to describe any colour on a TV, computer or phone.
  • In the HSB colour model:
    • Hue refers to the perceived difference between one colour and another and accounts for colour names such as red, yellow, green or blue.
      • Hue can be measured as a location on the standard colour wheel and expressed in degrees between 0 and 360.
    • Saturation refers to the perceived difference between one colour and another in terms of vividness.
      • Saturation is measured between a fully saturated colour (100%) and an unsaturated colour that appears dull and washed out until all colour disappears leaving only a monochromatic grey tone (0%).
      • A fully saturated colour is produced by a single wavelength or a narrow band of wavelengths.
      • On HSB colour wheels, saturation increases from the centre to the edge.
    • Brightness (colour brightness) refers to the difference between the way a colour appears to an observer in well-lit conditions compared with its subdued appearance when in shadow or when poorly illuminated.
Brightness, Intensity, amplitude

In this dictionary:

    • Brightness is used in connection with the perception of colour.
    • Intensity is used in connection with the amount of light that is produced by or falls on an object.
    • Amplitude is used in connection with the properties of electromagnetic waves.
Colour brightness and light intensity
  • The perception of colour in the world around us depends on the spread of wavelengths that reach the eyes of an observer. Red has a long wavelength, violet has a short wavelength.
  • The perception of the brightness of a colour depends on the intensity of the light an object emits (a light source) or reflects (a surface).
  • The intensity of light depends on the amplitude of the light wave that produces it.
  • Amplitude measures the height of light waves from trough to peak.
  • The amplitude of a light wave can be thought of in terms of the volume of photons that it carries.
  • Increasing the amplitude of a wavelength of light means the volume of photons falling on an object will increase its apparent brightness to an observer.