Colour brightness can be thought of as 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 colour brightness
- In this resource, the term colour brightness is used to refer to how things appear to a human observer in terms of their perception of colour.
- Colour is what humans see in the presence of radiated or reflected light.
- The brightness of the colour of an object or surface (its colour brightness) depends on the wavelengths and intensity of light that falls on it and the amount it reflects.
- The colour brightness of a transparent or translucent medium may depend on the wavelengths and intensity of light that falls on it and the amount it transmits or reflects.
- Colour brightness often depends on 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.
- The impression of colour brightness is also affected by hue because some hues appear brighter than others to human observers. So a fully saturated yellow may appear relatively brighter than a fully saturated red or blue.
About colour models
A colour model is the how-to part of a 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 brightness and colour models
- The term brightness is often used in association 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, so when we change from one colour model to another it’s best to change our terminology as well.
About colour theory
Colour theories underpin colour management by seeking to explain how human beings perceive colour and establish the rational basis for practical how-to methods for managing colour in different situations.
A system of colour management may be associated with:
- A colour theory
- A colour model
- Colour notation
- A colour space
- Colour wheel/s, colour picker/s
- Colour swatch/es, colour sample/s
- Colour profile/s for digital workspaces, monitors, printers etc.
The aspect of colour theory concerned with the human perception of colour aims to answer questions about:
- How our eyes register colour when exposed to light.
- The way our eyes and brains work together to produce the complex colour perceptions that make up the visible world.
- The part of the electromagnetic spectrum that is related to colour and how our eyes respond to different wavelengths of light.
- The fact that red, green and blue lights combined in different proportions can produce the impression of all the colours of the visible spectrum.
- The way colours appear in different situations such as in low or bright light and under artificial lighting.
- Human responses to different combinations of colour such as analogous, complementary and contrasting colours.
- The differences between the scientific, technical and creative understandings and descriptions of colour.
- Understanding the differences between:
The aspect of colour theory concerned with how-to methods for managing colour in different situations aims to answer questions about:
- The differences between mixing coloured lights, pigment or inks.
- Mixing and managing ranges (gamuts) of colours in logical, predictable and repeatable ways.
- Identifying and mixing particular colours in predictable and repeatable ways.
- Specifying colours using names, codes, notation, equations etc.
- The difference between additive and subtractive colour mixing.
- Systems and rules for mixing different and applying them to different materials such as fabrics, interiors and vehicles.
- Creating colour palettes, gamuts and colour guides.
- Managing the consistent reproduction of digital colour from start to finish.
Distinct colour theories are evident in:
- Trichromatic colour theory
- Opponent colour theory
- Neurological research
- Subtractive and additive theories of colour
- The Munsell colour system
- LAB colour model
- Spectral colour model
- RGB colour model
- HSB colour model
- CMY colour model
- Pantone Matching System (PMS) is a standardised system for the colour printing industry.
- RAL classic colour system is used mainly for powder coating, varnish, and plastic colouring.
About the HSB colour model
- The difference between the RGB and HSB colour models is limited to 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 is popular because it provides an intuitive way to select and adjust colours in software applications used for graphic design, web development and photography.
- Whilst RGB relies on adjusting the amount of red, green and blue needed to produce other colours the HSB colour model relies on adjusting hue, saturation and brightness.
- Both the RGB and 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 is usually described by using names such as red, yellow, green or blue.
- Hue can be measured as a location on an HSB colour wheel and expressed as a degree between 00 and 3600.
- 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.
- 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.
About brightness, intensity and amplitude
In this resource:
- Brightness is used in connection with light and so with the amount, or intensity, of light an object emits.
- Colour 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 and the amount of energy they carry.
About colour brightness & 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.
- Every colour (eg. red, magenta or violet) can be defined in terms of its hue, saturation and brightness.
- Saturated colours are produced by a single wavelength of light or a narrow band of wavelengths.
- The perception of the brightness of a hue depends on the intensity of the light a light source emits (a coloured light bulb for example) or the amount of light reflected off a coloured surface.
- The intensity of light, along with factors such as phase and interference, are directly related to the amplitude of an electromagnetic wave.
- Amplitude measures the height of light waves from the centre-line of a waveform to its crest or to a corresponding trough.
- Colour brightness, light intensity and amplitude of a light wave can all be thought of in terms of the volume of photons that strike the eye of an observer.
- So 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.