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 in general terms
  • The brightness of light depends on the intensity or the amount of light an object ( eg. the Sun or a lightbulb) emits.
  • The brightness of the colour of an object or surface depends on the intensity of light that falls on it and the amount it reflects.
  • The brightness of the colour of a transparent or translucent medium depends on the intensity of light that falls on it and the amount it transmits.
  • Because brightness is related to intensity, it is related to the amplitude of electromagnetic waves.
  • Brightness is influenced by the way the human eye responds to the colours associated with different wavelengths of light. For example, yellow appears relatively brighter than reds or blues to an observer.
About brightness and colour models
  • 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 colour 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.
About 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
  • We often get by using basic colour names like red, yellow and blue but know how to slip into a broader vocabulary of names when we need them 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 rational approach that deals with all the different ways that colour behaves as we move from one situation or medium to another.
About the 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.

  • The only difference between the RGB and HSB colour models is the way colours are represented in terms of colour notation and dealt with in software and apps.
  • Both the HSB and RGB colour models deal with how to mix 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 is usually shown to increase from the centre to the circumference.
    • 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, intensity and 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.
About 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 any 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 usually measures the height of light waves from the centre-line of a waveform to its crest.
    • 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.