Brightness

Brightness refers to the perceived difference between a colour observed in ideal sunlit conditions compared with conditions where the vitality of the hue is lost because the lighting is poor.

Associating brightness with a colour model

To avoid confusion about the term brightness it is best to associate it with a colour model, a practical application and a family of related terms.

  • Examples of colour models include spectral colour, RGB colour, CMYK colour and HSB colour.
  • Examples of practical applications include digital design, stage lighting, mixing of oil or water-based paints, inks and dyes.

Colour in general terms

  • When an observer asks themselves what colour something is, they might refer to spectral colours and use names associated with rainbows (ROYGBV), to a set of colours (a palette of colours) they are working with or to a family of colours such as warm or cool colours.
  • 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.

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.
  • These days, the most practical colour models are built into applications such as Adobe Creative Cloud which allow easy digital output to TV’s, computers and phones or printing onto paper and other surfaces.
  • Widely used colour models include:
    • Spectral colour
    • RGB colour
    • HSB colour
    • CMYK colour

Using the term saturation

  • At lightcolourvision.org we use brightness in relation to the colour models it belongs to. One of our favourites is the HSB colour model.
  • Colour models describe the attributes of colour in different ways.
  • The HSB colour model refers to saturation alongside hue and saturation.
  • 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 uses a different set of attributes because one of its main concerns is how coloured inks appear on paper. Because saturation isn’t part of the vocabulary used in that field the term is best avoided.

Colour brightness and light intensity

  • The perception of hue in the world around us depends on the spread of wavelengths that reach the eyes of an observer. Wavelength is a measure of the the distance between the peaks of a wave.
  • The  perception of brightness of a hue in the world around us depends on the amount of light an object emits or reflects. Brightness depends on the amplitude of the oscillation of light waves. Amplitude or intensity is a measure of the height of light waves from trough to peak.
  • The amplitude or intensity of a light wave can be though of in terms of the volume of photons that it carries.
  • Increasing the amplitude of a wavelength of light and so the volume of photons falling on an object will increase its apparent brightness to an observer.

HSB colour model

  • The HSB colour model provides an intuitive way to select and adjust colours in software applications used for graphic design, web development and photography.
  • HSB describes the fundamental characteristics of how colours appear when reflected by or transmitted through an object towards an observer as:
    • Hue refers to the perceived difference between one colour and another by using names such as red, yellow, green or blue. Hue can be measured as a location on the standard colour wheel and expressed as a degree 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 appear dull and washed out until all colour disappears leaving only a monochromatic grey tone (0%). On many colour wheels, saturation increases from the centre to the edge.
    • Brightness refers to the perceived difference between a colour observed in ideal sunlit conditions compared with conditions where the vitality of the hue is lost because the lighting is poor. Brightness can be measured as a percentage from 100% to 0%. As the brightness of a fully saturated hue decreases it appears progressively darker.