Dictionary of light, colour & vision

About additive & RGB colour The RGB colour model used by TV, computer and phone screens involves additive colour mixing. The RGB colour model produces all the colours seen by ...

About additive and subtractive colour models There are two main types of colour models, additive and subtractive. Additive Colour Models Additive colour models are used when blending light to produce ...

About Adobe RGB, ProPhoto RGB & sRGB The most common colour profiles in photography are sRGB, Adobe RGB (1998), and ProPhoto RGB. Adobe RGB, developed in 1998, consists of the ...

About amacrine cell functions Amacrine cells are a type of neuron found in the retina, the light-sensitive tissue lining the back of the human eye. They play a critical role ...

About amplitude, brightness, colour brightness and intensity The terms amplitude, brightness, colour brightness and intensity are easily confused. In this resource: Amplitude Amplitude refers to the amount of energy carried ...

Awaiting final edit About atoms as a light source An atom isn't typically considered a light source in the conventional sense because it can't generate light spontaneously. In its "ground ...

About bands of colour, spectral and non-spectral colours Bands of colour Bands of colour are composed of a continuous range of wavelengths, so for example: A continuous range of wavelengths ...

About brightness In this resource, the term brightness is associated with the intensity of light an object such as the Sun or a lightbulb emits. In everyday experience, we often ...

About brightness & colour models The term brightness is often used in association with a specific colour model. Examples of colour models include: HSB colour model Spectral colour model RGB ...

About centre-surround antagonism Centre-surround antagonism refers to the way retinal neurons organize their receptive fields. Centre-surround antagonism refers to the way that light striking the human retina is processed by ...

About chromatic adaption Chromatic adaptation refers to the ability of our visual system to adjust to changes in lighting conditions, helping to keep the perceived colour of objects relatively stable ...

About chromophores Things appear to have colour because they absorb some wavelengths of light and reflect others. Chromophores are the part of molecules responsible for the absorption and reflection of ...

About the CMY colour model and colour perception A good starting point for understanding the CMY colour model is trichromatic colour theory. Trichromatic colour theory explains the underlying physiological basis ...

About CMY colour printing CMY printing involves mixtures of three primary colours of dyes or inks - cyan (C), magenta (M) and yellow (Y). There are two distinct types of ...

About subtractive colour printing in practice CMY printing involves three translucent inks corresponding with the primary colours - cyan, magenta and yellow. The CMY colour model is subtractive in the ...

About colour & visual perception Colour is not a property of electromagnetic radiation, but rather a characteristic of visual perception. The human eye, and therefore human perception, is sensitive to ...

About colour brightness In this resource, the term colour brightness is used to describe how things appear to a human observer in terms of their perception of colour. Colour is ...

About colour brightness & light intensity The perception of colour depends on the wavelengths that reach an observer's eyes. Red has a longer wavelength, while violet has a shorter wavelength ...

About colour management & photographic workflow In photography, the main goal of colour management is to control the accurate capture of original colours and ensure consistent reproduction of specific colours ...

About colour management in practice A typical colour management workflow starts by ensuring that colours seen through a camera viewfinder are captured and digitally recorded. Editing software such as Adobe ...

About colour models A colour model derived from colour theory enables a more precise and reproducible method of representing and working with colour. Colour models are a practical application of ...

About colour models and colour wheels Colour wheels are used to represent colour models that can generate a complete range (gamut) of colours using three primary colours. These models include: ...

About the colour of objects Objects are composed of atoms, which bond together to form molecules, elements, and compounds. These different combinations of atoms give objects their unique properties and ...

About the perception of colour The perception of colour is a highly subjective experience. The colour of nearby objects can influence colour perception. The environment in which colours are observed ...

About colour spaces & examples A colour space aims to accurately define the relationship between any selected colour within a colour model and how it will appear when it is ...

About colour theories, models, spaces and management systems Colour theory, colour models, colour spaces, and colour management systems are integral to understanding, representing, and manipulating colour in various fields. Colour ...

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 ...

About complementary colours & colour wheels Complementary colours are always opposite one another on a colour wheel. The complementary colour of a primary colour is always a secondary colour on ...

About complementary colours & the RGB colour model When using the RGB colour model, the primary/secondary pairs of complementary colours are red-cyan, green-magenta and blue-yellow. Combining the wavelengths corresponding with ...

About diagrams at lightcolourvision.org Diagrams play a significant role in creating mental representations of knowledge domains. They are widely used in various fields, including science, engineering, and mathematics. A mental representation is ...

About electric charge Electric charge is the physical property of matter that causes it to experience a force when it interacts with an electromagnetic field. An electric charge can be ...

About electric charge and energy in an atom An atom has a set number of particles that determines what kind of element they are. Each element has a specific number ...

About Electromagnetism & interactions: Terms ...

Electrostatic & magnetic force The electrostatic and magnetic forces are two aspects of the same force and very closely related to each other. The electromagnetic force is the fundamental interaction ...

About geometrical optics Geometrical optics, also known as ray optics, is one of the two main branches of optics, the other being physical optics. Geometrical optics is based on the ...

About heating atoms to produce light When heat excites atoms, the electrons around the nucleus change their energy levels and behaviour. Here is an outline of the process: Energy Levels ...

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 main ...

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

About the HSB colour model and saturation The HSB colour model, like the RGB colour model, is an additive colour model used to mix light. The RGB and HSB colour ...

HSL and HSV are the two most common cylindrical-coordinate representations of points in an RGB color model. Developed in the 1970s for computer graphics applications, HSL and HSV are used today in color pickers, in image editing software, and less commonly ...

About hue and colour models Hue refers to the attribute of a colour that allows us to distinguish it from others on the colour spectrum, and it is a fundamental ...

About the term hue here at lightcolourvision.org At lightcolourvision.org we use hue in relation to the colour models it belongs to. Colour models describe the attributes of colour in different ...

About the human eye, light and RGB colour The human eye, and so human perception, is tuned to the range of wavelengths of light that make up the visible spectrum ...

About Interference patterns Two waves meeting on a pond is a classic example of wave interference. When two waves overlap, their crests and troughs can interact in two ways: Constructive ...

About interneurons Interneurons are also referred to as relay neurons, connector neurons, intermediate neurons and local circuit neurons each of which helps to explain their function. Interneurons form nodes within ...

About interneurons and the human eye There are four types of interneurons in the human eye: They are the amacrine cell, bipolar cell, horizontal cell and Müller cell. Interneurons in ...

About the laws of reflection When light reflects off a surface or object, it behaves predictably, following three laws known as the laws of reflection. The three laws of reflection ...

About light and colour light Light travels at a speed of 299,792,458 meters per second in a vacuum, but its speed decreases when it passes through a medium rather than ...

About light-waves & particles Electromagnetic radiation and the electromagnetic energy it transports can be described in terms of waves. Electromagnetic radiation (radiant energy) includes all wavelengths of light from radio ...

About light, colour & vision Light The human eye and human vision are adapted and responsive to the visible spectrum, which includes wavelengths of light corresponding to colours ranging from ...

About light, radiation, radiant energy & electromagnetic energy There is a difference in meaning between the terms light, electromagnetic radiation, radiant energy and electromagnetic energy in physics. Light Light is ...

About lines that are normal to one another If one line is normal to another, then they are at right angles to one another. In geometry, a normal (or the ...

ABOUT LUMINOSITY & LUMINANCE Luminosity signifies the total amount of visible light emitted by a light source and is measured in watts or lumens. It is a measure of the ...

About the anatomy of neurons Neurons are the building blocks of the nervous system. A typical neuron consists of a cell body (soma), dendrites, and a single axon. Dendrites and ...

About neurons and the human retina There are two principal types of neurons in the retina of the human eye: the rod and cone photoreceptors and ganglion cells. There are ...

About the observation of colour The human eye is sensitive to the visible spectrum, which includes all the spectral colours ranging from approximately 400 to 700 nanometers. The sensitivity of ...

About particles & diagram conventions Absorption: When a photon is absorbed by an atom or molecule, it can be depicted in a diagram by showing the photon arrow disappearing and ...

About the energy in photons According to the equation: E = hf, the amount of energy photons possess is directly proportional to their frequency (f) and inversely proportional to their ...

About the properties of photons A photon is a type of elementary particle that is a quantum (plural = quanta) of the electromagnetic field. This means that it is the ...

About photons and electric fields An electric field describes the influence a charged object exerts on other charged objects in its vicinity. It possesses both magnitude and direction. Created by ...

About photons & electrons Photons are fundamental particles and are considered to be the primary constituent of visible light and all other types of electromagnetic radiation. Photons are considered to ...

About photons, electric and magnetic fields Photons are the elementary particles of electromagnetic radiation. They are quanta or discrete packets of energy that make up electromagnetic waves. Electromagnetic waves are ...

About plane polarization & rainbows Plane polarization is one of the optical effects that account for the appearance of rainbows. Plane polarization, also known as linear polarization, is a characteristic ...

About pure & vivid colours Pure colours A pure colour is a single unique spectral colour and so a fully saturated colour produced by a single wavelength of light. In ...

About quantum fields In modern physics, the underlying substance that is believed to unify matter and energy is called a "field". A field is a physical entity that fills space ...

About rainbows and bands of colour There are several reasons why an observer looking at phenomena like rainbows perceives bands of colour. The human perceptual system tends to simplify colour ...

About rainbows, raindrops & angles Viewing angle refers to the number of degrees through which an observer must move their eyes or turn their head to see a specific colour ...

About red, green & blue light Because of the way the eye works, we can see all the colours of the visible spectrum by mixing red, green and blue lights ...

About RGB & the trichromatic colour model To make sense of the physiological basis of the RGB colour model we can relate it to how the trichromatic colour model explains ...

About RGB colour and colour perception The human eye, and so visual perception, is tuned to the visible spectrum and so to spectral colours between red and violet. RGB colour ...

About the RGB colour model in practice RGB colour model works in practice by asking three questions of any colour: how red it is (R), how green it is (G), ...

About RGB colour notation RGB colour values are expressed as decimal triplets (yellow = 255, 255, 0) or hexadecimal triplets (green = #00FF00). Computer software is programmed to recognise RGB ...

About the RGB colour space The Adobe RGB (1998) colour space is designed to encompass the colours that can be output by CMYK colour printers. When the RGB colour model ...

About RGB colour values RGB colour values are represented as decimal triplets (e.g., yellow = 255, 255, 0) or hexadecimal triplets (e.g., green = #00FF00). These values are used by ...

About RGB colour wheels & intermediate colours Intermediate colours on an RGB colour wheel are produced by mixing equal intensities of adjacent pairs of colours. Secondary colours are created by ...

About RGB secondary colours RGB secondary colours are the hues formed by combining two primary colours of light in equal proportions. The three RGB secondary colours are cyan, magenta, and ...

About saturation & wavelength Saturation is one of the three primary properties of colour, alongside hue and brightness. A colour looks saturated when made by a single or a small ...

About saturation and colour models The concept of saturation is most comprehensible when connected to a particular colour model. Examples of colour models include: CMY colour model HSB colour model ...

About scattering in physics Rayleigh scattering Rayleigh scattering occurs when visible light or other forms of electromagnetic radiation are scattered by particles smaller than their own wavelength. Mie scattering Mie ...

About scattering in raindrops Regular scattering, caused by refraction and chromatic dispersion, is responsible for the colours seen in rainbows. Refraction occurs when light changes speed and direction as it ...

About random scattering Random scattering Random scattering occurs when a material, due to irregularities or imperfections on its surface, reflects or transmits light rays in various unpredictable directions. This scattering ...

About regular scattering Regular scattering happens when light bounces off a smooth, curved surface in a predictable way, creating a clear and undistorted image. Think about a spoon in a ...

About seeing in colour When an observer considers the colour of something, they might refer to: Spectral colours and use names commonly associated with rainbows (ROYGBV). A specific colour model ...

About shells & orbitals Shells Think of shells as regions around the nucleus where electrons are most likely to be found. These regions are like "zones" or "areas" within the ...

About space, time & matter Space, time, and matter are intimately related concepts in physics, and our understanding of their interplay has evolved significantly over the past few centuries. Space ...

About speed & velocity Speed and velocity are not the same. While they are related, there is a key difference between the two: Speed is a scalar quantity that refers ...

About the speed of light The speed of light, 299,792,458 meters per second, is the maximum speed at which information can be transmitted through space. The fact that the speed ...

About the speed of light and black holes The speed of light squared (c^2) is related to the energy required to create a black hole through Einstein's famous equation E=mc^2, ...

About the speed of light and Planck scale The Planck scale is the scale at which the effects of gravity are expected to become comparable to the other fundamental forces ...

About the speed of light waves & photons Speed of light waves The speed of a light wave is a measurement of how far it travels in a certain time ...

About the subjective experience of colour The perception of colour is a highly subjective experience. Several factors determine the specific colour an observer sees, including: The environment in which colours ...

About subtractive colour on screen Computers, TVs and phones use the additive RGB colour model to represent colour. It's called additive because it works by adding different coloured lights together ...

About sunlight & nuclear fusion The Sun generates electromagnetic waves primarily through nuclear fusion. Here's a step-by-step explanation: Nuclear fusion At the Sun's core, extremely high temperatures and pressure allow ...

About Temperature & colour The surface colour of objects and their thermal temperature can be distinguished as follows. Surface colour The surface colour of an object seen by an observer ...

About the normal, angles of incidence, reflection & refraction The angles of incidence, reflection and refraction are measured between a ray of light and an imaginary line called the normal ...

About trichromatic colour vision (Trichromacy) Trichromatic colour theory explains how the human eye perceives colour. Trichromatic colour theory is based on the existence of three types of light-sensitive cone cells ...

About viewing angles, angular distance and angles of deflection The term viewing angle refers to the angle, measured in degrees, between the direction an observer looks in to see the ...

About wave diagram conventions Absorption: Absorption is the process by which a material absorbs some or all of the energy of light. This can be represented by a decrease in ...

About wavelength, frequency & amplitude The wavelength of light is always inversely proportional to its frequency, so if one increases, then the other decreases. Wavelength represents the distance between two ...

About wavelengths of light and colour vision There is a clear difference between the wavelengths of light that make up the visible spectrum and how the human eye converts the ...

About waves in water When you throw a stone into a pond, it creates a series of ripples, or waves, that propagate outward in concentric circles until they encounter obstacles ...

About white light White light is the term for light that contains all wavelengths of the visible spectrum at the same intensity. The term 'white light' doesn't imply that light ...

About why we use colour models Colour models help to relate and coordinated colours with one another when working with different light sources, media such as paints or inks, objects ...