The terms brightness and colour brightness have distinct meanings. The first refers to a property of light, and the second to a property of colour as detailed below.
- Brightness (as opposed to colour brightness) is used to refer to a property of light.
- Colour brightness is used to refer to how much colour something appears to emit or reflect towards an observer.
- Colour brightness can be understood as the variation in how a colour is perceived by an observer under well-lit conditions compared to its more muted appearance when in shadow or under poor illumination.
- In the HSB colour model:
- Hue refers to the perceived difference between colours and is usually described using names such as red, yellow, green, or blue.
- Saturation refers to the vividness of a colour compared to an unsaturated colour.
- Brightness refers to the perceived difference in the appearance of colours under ideal sunlit conditions compared to poor lighting conditions where a hue’s vitality is lost.
- Brightness can be measured as a percentage from 100% to 0%.
- As the brightness of a fully saturated hue decreases, it appears progressively darker and achromatic.