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Glossaries
Glossaries
International lighting vocabulary (Commission Internationale de l’Eclairage [CIE])
https://cie.co.at/e-ilv (online version of the ILV)
The CIE International Lighting Vocabulary, first published in 1938 and revised periodically since then, gives definitions for more than 1400 terms and is by far the most comprehensive and authoritative source on the scientific terminology of light and colour. Although previously very expensive and limited in distribution, it is now freely available online as the e-ilv.
The dimensions of colour - Glossary (David Briggs)
Concise, partly illustrated glossary of colour terms, with emphasis on terms relevant to painters.
For additional online glossaries see 12 Further Information.
What is a Colour?
What is a Colour?
The Commission Internationale de l'Eclairage (CIE) International Lighting Vocabulary recognizes and defines two distinct senses of the word colour: perceived colour and psychophysical colour:
colour (perceived) (CIE)
A perceived colour is defined as a "characteristic of visual perception that can be described by attributes of hue, brightness (or lightness) and colourfulness (or saturation or chroma)", for example light greyish red.
"A perceived colour such as red or white or green is the way in which we perceive the spectral composition of a light or the intrinsic spectral reflectance of an object" (What is a Colour?). Perceived colour is however additionally influenced by "the size, shape, structure and surround of the stimulus area, on the state of adaptation of the observer's visual system, and on the observer's experience of the prevailing and similar situations of observation".
colour (psychophysical) (CIE)
A psychophysical colour is defined as a "specification of a colour stimulus in terms of operationally defined values, such as 3 tristimulus values", for example R 180 G 108 B 108 in a given RGB colour space .
A psychophysical colour specifies the perceivable property of a spectral composition or reflectance. This depends in part on the visual system of the observer: for a trichromatic observer this perceivable property involves the overall amounts of three (long-, middle- and short-wavelength) components of the spectral distribution concerned (What is a Colour?).
Two physically different stimuli with the same psychophysical colour specification (for example R 180 G 108 B 108 in a given RGB space on two different kinds of screens) will match in perceived colour for a "standard" observer when viewed in the same conditions, but the perceived colour of this matching pair will vary depending on those conditions (in the above example, the perceived colour will vary greatly depending on whether the two screens are viewed indoors or outdoors in sunlight) .
The word "colour" is also used in several other senses colloquially or by individual authors. Paul Green-Armytage (2006) distinguished five such additional "kinds of thing that colours are variously understood to be": conventional colour, substance colour, formula colour, spectral profile colour and inherent colour. For example when artists loosely speak of their paints as "colours" and of mixing paints as "mixing colours" the word "colour" is being used in the sense Green-Armytage identifies as substance colour.
Last but not least, contemporary philosophers hold a diverse range of positions on the fundamental nature of colour (colour ontology); for an introduction to these views see the links below.
Colour subjectivisms: What, why, and which one? (Derek H. Brown)
Dr Derek Brown discusses the forthcoming "Routledge Handbook of Philosophy of Colour", co-edited by himself and Professor Fiona Macpherson, both from the Department of Philosophy and the Centre for the Study of Perceptual Experience at the University of Glasgow, and then presents a very accessible overview of philosophy of colour.
What is a colour? Scientific opinion about colour and colour measurement (David Briggs)
The video explains and illustrates the concepts of perceived and psychophysical colour, along with the colour-related terms of spectral distribution, metameric colour stimuli, spectral reflectance, object colour, tristimulus values including CIE XYZ, the CIE xy chromaticity diagram and xyY colour space, and the psychophysical parameters of dominant wavelength and purity.
Color (Stanford Encyclopaedia of Philosophy)
Color (Internet Encyclopaedia of Philosophy)
Color (PhilPapers)
Attributes of Perceived Colour
Attributes of Perceived Colour
In the image on the left we perceive a cube having a uniform orange colour belonging to it, as if it were painted all over with an orange paint of the same hue, lightness and chroma (around Munsell 10R 6/14). The object-colour attributes of lightness and chroma are perceived as belonging to an object because they exhibit a tendency towards stability, called colour constancy, under varying viewing conditons, especially varying intensities of the same illumination. In contrast, planes A to C appear successively brighter and more colourful, but this varying brightness and colourfulness is perceived as being imposed by the illumination rather than as belonging to the object itself; they describe the varying appearance of the light reaching our eyes from different areas of the object. Similarly, we perceive the lighter-coloured areas of the floor as being white things of uniform high lightness, yet at the same time the light from these areas varies greatly in brightness. When we can freely examine an object in daylight, the colour we perceive as belonging to it (and might understandably consider to be its seemingly intrinsic colour) is usually a good indication of the overall spectral reflectance of the object at the level of its long-, middle and short-wavelength components, as perceivable to the human visual system.
The CIE e-ilv currently recognizes and defines six attributes of perceived colour: hue, brightness, lightness, colourfulness, saturation and chroma. A seventh attribute of perceived colour, comprising blackness and its inverse brilliance, is featured in some other systems.
The Elements of Colour (David Briggs)
The Elements of Colour is an online presentation I gave on May 18, 2023, for the Design Institute of Australia, focusing on the first of my two papers recently accepted for the Journal of the International Colour Association. The first part of the presentation provides illustrated explanations of eight attributes or dimensions of perceived colour - hue, lightness, chroma, brightness, colourfulness, saturation, blackness and brilliance - and the second part examines the connections between colour stimuli, colour perceptions and colour measurement to address the question of "what is a colour?". The third part gives an overview of some of the illustrations from the second paper, which analyzes colour perception in greater depth by discussing the major modes of colour appearance and the attributes of perceived colour and their interconnections in more detail. I recommend this presentation as an introduction to some of the most fundamental yet widely misunderstood concepts relating to colour.
How Many Dimensions Are Required to Describe Color Appearance? (Mark Fairchild)
https://web.archive.org/web/20191229063612/https://rit-mcsl.org/fairchild//WhyIsColor/Questions/4-8.html (hint: not 3!)
hue (CIE)
Hue is defined in the e-ilv as the "attribute of a visual perception according to which an area appears to be similar to one of the colours: red, yellow, green, and blue, or to a combination of adjacent pairs of these colours considered in a closed ring". This closed ring of hue perceptions can be represented on many different hue scales or "colour wheels".
unique hue (CIE)
" hue that cannot be further described by the use of hue names other than its own. Equivalent term: 'unitary hue'. NOTE There are 4 unique hues: red, green, yellow and blue forming 2 pairs of opponent hues: red and green, yellow and blue."
The CIE definitions of hue and unique hue acknowledge Ewald Hering's concept of hue opponency. Outside the CIE system this concept is also foundation of hue specification in the Natural Colour System (NCS).
A. Generic opponent hue scale based on even spacing of the four unique hues. B: Munsell hue scale, based perceptually even spacing, showing locations of the hues conventionally regarded as middle red, yellow green and blue in naming artists's paints.. C: Traditional colour wheel of Itten (1961; 1973 edn).. Eliminating green as a primary and spacing middle red, yellow and blue symmetrically makes this scale very uneven perceptually. After Briggs, Where is Colour Education Now? (2018).
lightness (of a related colour) (CIE)
Lightness is defined in the e-ilv at the "brightness of an area judged relative to the brightness of a similarly illuminated area that appears to be white or highly transmitting. NOTE Only related colours exhibit lightness."
Lightness refers to the scale of visual appearance from black through various shades of grey to white (or transparent and colourless).
chroma (CIE)
Chroma is defined in the e-ilv as the "colourfulness of an area judged as a proportion of the brightness of a similarly illuminated area that appears white or highly transmitting". Chroma is in effect the departure of a colour from a grey of the same lightness (http://www.huevaluechroma.com/121.php#chroma). Chromaticness is a measure of chroma relative to a perceived full chroma employed in the NCS.
brightness (CIE)
Brightness is defined in the e-ilv as the "attribute of a visual perception according to which an area appears to emit, or reflect, more or less light."
Brightness is our perception of the amount of light emitted or reflected by an area. It does not have a definite upper limit the way lightness has an upper limit of white. A white object appears brighter in light than in shadow.
The term dim refers to low levels of brightness (https://cie.co.at/eilvterm/17-22-062). Usually lights are described as "bright" or "dim" whereas surface colours are described as "light" or "dark", but, this distinction is not universal (https://cie.co.at/eilvterm/17-22-061).
colourfulness (CIE)
Colourfulness is defined in the e-ilv as the "attribute of a visual perception according to which the perceived colour of an area appears to be more or less chromatic". A note associated with the definition in effect says that a given coloured object will exhibit more colourfulness as it is more strongly lit unless the brightness is very high.
saturation (CIE)
Saturation is defined in the e-ilv as the "colourfulness of an area judged in proportion to its brightness". Saturation in this formal sense is in effect the perceived concentration of the chromatic as opposed to the white component of the light coming from the area. The word "saturation" is used in quite different senses in some digital colour spaces and other systems, and colloquially is widely used as a generic term for chromatic intensity in contexts where chroma, colourfulness, saturation and other aspects of chromatic intensity are not distinguished (http://www.huevaluechroma.com/121.php#saturation)
Illustration of lightness, chroma, brightness, colourfulness and saturation from The Dimensions of Colour (David Briggs)
The perception of color as espoused by Ralph M. Evans of the Eastman Kodak Company and its extension to what is known now and what remains to be seen (R. L. Heckaman and Mark D. Fairchild, Rochester Institute of Technology)
https://pdfs.semanticscholar.org/32b5/8d6ad3a1da626baa2345d860fed23ced37b6.pdf
Reviews Ralph Evans' concept of brilliance from his last book, The Perception of Color (1974). Brilliance is the relative brightness of an area judged on a scale of appearance proceeding from black through decreasing blackness (Evans' "greyness") to fluorent (fluorescent-looking) and then self-luminous. It's inverse, called blackness, is a scale of perceived black content in an object colour found in the Scandinavian Natural Colour System (NCS) and other systems.
In this image created by R. Beau Lotto, two physically matching image areas evoke a dimly-lit tile exhibiting fluorence on the near face and a strongly lit tile exhibiting moderate blackness on the top face. It is remarkably difficult to see that these two image areas match unless a reference perceived to be outside the scene lighting is included (right) or the rest of the image is masked (see "Illusion 3" here)
Psychological color order systems (Rolf Kuehni and Andreas Schwarz)
A large part of Chapter 5 from Kuehni and Schwarz's outstanding book Color Ordered (2008) is available online on Google Books, including some excellent descriptions and diagrams explaining the colour attributes of hue, lightness, absolute lightness, relative lightness, saturation, chroma, chromatic content, blackness content and whiteness content.
Diagrams showing lines of equal lightness, (top left), chroma (top right), saturation (bottom left) and blackness (bottom right) on a generic object-colour hue page from Color Ordered: A Survey of Color Systems from Antiquity to the Present by Rolf G. Kuehni, Andreas Schwarz (2008). Source: Google Books preview.
The dimensions of colour: The dimensions introduced (David Briggs)
http://www.huevaluechroma.com/013.php (lightness)
http://www.huevaluechroma.com/016.php (brightness and colourfulness)
http://www.huevaluechroma.com/017.php (saturation)
http://www.huevaluechroma.com/018.php (blackness and brilliance)
Some of the purely verbal definitions and brief accompanying notes and formulae in the e-ILV can be difficult to understand for non-specialists. These web pages and the linked videos explain and illustrate the definitions of the six fundamental attributes of perceived colour defined therein.
Dimensions of color for artists (David Briggs)
colormaking attributes (Bruce MacEvoy)
Bruce MacEvoy's take on the perceived colour attributes of hue, brightness, lightness, colourfulness, saturation, chroma and brilliance on his extensive "Handprint" website.
Hue, Lightness and Chroma
Hue, Lightness and Chroma
This widely used set of perceived-colour attributes is known both from its quantitative manifestations in the Munsell System, the L*Ch representation of CIE L*a*b*space, and the RAL D4 Colour Atlas, and as the generic qualitative framework used by many artists and designers (for whom the concept of chroma often goes by the name "saturation" - see below). For many additional links specific to the Munsell System see the entry for that system on the Colour Order Systems page.
While one could describe colours in terms of hue, lightness and saturation in their scientific senses, it is usually clear when this combination of terms is encountered that the word "saturation" is intended to mean chroma rather than saturation as defined in standard CIE terminology. An exception is in the commonly used digital colour space called either HSB or HSV ("hue, saturation and brightness/value" ), where the the "S" is a measure of relative saturation rather than chroma. (In another space called HLS for "hue, lightness and saturation", the "S" stands for a measure of relative chroma. For the meanings of so-called "lightness", "brightness" and "saturation" parameters in these spaces see the Dimensions of Colour entries on lightness and saturation).
The dimensions of colour - 1.1 Colours in space (David Briggs)
Colour theory in two minutes (Stephen Westland)
Two-minute videos explaining hue, lightness and chroma in simple terms.
Color Practice (Matias Dahl)
Interactive lightness and chroma sorting exercise available online and as iPad app
Interactive colour demos (Stephen Westland and Marjan Vazirian)
Interactive online demonstrations of hue, lightness and chroma.
Hue and Blackness/Whiteness/Chromaticness
Hue and Blackness/Whiteness/Chromaticness
A different set of perceived-colour attributes is employed in the popular generic classification of chromatic object colours into pure or full colours, tints (perceptually containing white), shades (perceptually containing black) and tones (perceptually containing both black and white), and correspondingly applied to paint mixtures according to their physical content of black and white paint components. This results in a triangular hue page in which colours are placed according to their relative proximity to pure colour (chromaticness), pure white (whiteness) and pure black (blackness). Versions of these attributes, specifically defined in different ways, are employed in the Scandinavian Natural Colour System (NCS) and in the historical Ostwald System.
Generic representation of the attributes of blackness, whiteness and chromaticness.
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