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This section concerns the attributes of colour as a perception (hue, lightness, chroma etc.), considered individually and as dimensions of perceptual colour spaces. Links concerned primarily with colorimetric and digital colour measures and spaces are listed in Section 4.
Perceptual Colour Attributes
Perceptual Colour Attributes
Definitions
Definitions
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 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. Some of the purely verbal definitions and brief accompanying notes and formulae in the e-ILV can be difficult for non-specialists to understand at first. The following web pages and the linked videos explain and illustrate the definitions of the six fundamental attributes of perceived colour defined therein.
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)
http://www.huevaluechroma.com/121.php (concise, partly illustrated glossary of colour terms, with emphasis on terms relevant to painters).
Dimensions of color for artists (David Briggs)
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!)
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.
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.
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: In this section I cover attributes and spaces of perceived colour and I cover psychophysical Ior colorimetric specifications in Section 4.
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)
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.
Hue
Hue
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
Lightness
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
Chroma
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
Brightness
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
Colourfulness
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
Saturation
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)
Blackness, Whiteness and Chromaticness
Blackness, Whiteness and Chromaticness
A different set of perceived-colour attributes is employed in the popular 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.
Brilliance
Brilliance
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)
Perceptual Colour Order Systems
Perceptual Colour Order Systems
Definitions
Definitions
colour order system (CIE)
"arrangement of samples according to a set of principles for the ordering and denotation of their colour, usually according to defined scales. NOTE A colour order system is usually exemplified by a set of physical samples, sometimes known as a colour atlas. This facilitates the communication of colour but is not a prerequisite for defining a colour order system".
colour atlas (CIE)
"collection of colour samples arranged and identified according to specified rules".
colour space (CIE)
"geometric representation of colour in space, usually of 3 dimensions".
In an alternative usage found particularly in the literature of Adobe Inc., the term color space is restricted to what the CIE calls a colorimetric colour space, and non-colorimetric colour spaces are referred to as color models.
colorimetric colour space (CIE)
"colour space defined by 3 colorimetric coordinates. NOTE CIE XYZ tristimulus values are colorimetric coordinates, as are RGB values that have an exact and invertible mathematical relationship to CIE XYZ tristimulus values". For definitions of the CIE colorimetric colour spaces see here.
Overviews
Overviews
Color museum (Narciso Silvestrini and Ernst Peter Fischer):
https://web.archive.org/web/20051231232111/http://www.colorsystem.com/
Major summary of colour classification systems from antiquity to the present day.
ColorAcademy - Classification (Don Pavey and Roy Osborne)
Linked pages describe systems including CIE, Munsell, NCS, Ostwald, Pantone and the British Standards Institution. (Website currently accessible only via archive.org Wayback Machine).
Lightness-based Colour Spaces
Lightness-based Colour Spaces
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.
Munsell System
Munsell System
The dimensions of colour (David Briggs)
http://www.huevaluechroma.com/011.php (overview)
http://www.huevaluechroma.com/013.php (lightness)
Munsell color system (Bruce MacEvoy)
Munsell.com (X-rite)
https://munsell.com/about-munsell-color/how-color-notation-works/
Blog with many articles relating to the Munsell system (not very active lately).
Colour Mixing Tools (Zsolt Kovacs-Vajna)
Suite of free programs comprising:
Color2Drop (a program to convert RGB, Lab or Munsell HVC color coordinates into paint mixing recipes)
Drop2Color (a program to visualize the color of mixed paint recipes)
RS2Color (a program to visualize the color of reflectance spectra)
RealPaint is a related set of tools for iOS, both for iPhone and iPad using iOS 9.0 or later, that includes a colour picker that displays values in very accurate Munsell coordinates along with sRGB, Display P3, CMYK, HSL, HSV/B, Lab, Lch-ab, Luv, Lch-uv, XYZ, and xyY. http://www.ai4res.com/realpaint.html
ChromaMagic (Michele Clamp)
Upload an image to find the nearest Munsell notation of a selected pixel. Now also available as an app for iPhone and android.
https://micheleclamp.com/the-munsell-color-system/ (clear introduction to the Munsell system)
ColorWell (John Morfis)
The Munsell Explorer find artists' oil paints by their rated Munsell notations and another tool generates shading series for any Munsell notation.
Color Translator & Analyzer (Babelcolor)
"CT&A (Color Translator & Analyzer) is a collection of tools specifically designed for the measurement, conversion, and analysis of individual colors or small batches of colors". Commercial software, but some operations work in demo mode, notably including bidirectional conversion between various RGB spaces and Munsell.
The digital Munsell (Gernot Hoffman)
A pdf of the colours of the Munsell Book of Color glossy edition,with CIE L*a*b* and sRGB conversions.
Munsell Conversion Software (WallkillColor): Features:
http://wallkillcolor.com/ (Windows, rentware)
Converts Munsell Notation to XYZ, L*a*b*, RGB, CMYK
Converts RGB to XYZ, L*a*b*, Munsell Notation - CIELAB correction for dark colors added
Displays Color on screen
Print pages to color Printer
Munsell Book of Color
Value Page that shows all Hues and Chromas for a constant value
Color Tolerance Page that displays a Munsell color with pairs of
lighter/darker, redder/greener and Yellower/Bluer
Image Analysis - Load a JPG picture and select spots to display Munsell Notation
Virtual Munsell Color Wheel (Andrew Werth)
Displays Munsell hue pages and sRGB values for each Munsell notation
Munsell Color Chart 2 (Ksgc, android/Windows app)
Displays Munsell hue pages and sRGB values for each Munsell notation
Virtual Atlas (VCS Consulting)
Among many other functions (see below), the Virtual Atlas can be used to convert from Munsell notations to a wide range of RGB spaces under different assumptions.
Munsell Color Palette (Andrew Geng)
Charting color from the eye of the beholder (Landa and Fairchild): Reprint of American Scientist article on Munsell and the Munsell system.
https://web.archive.org/web/20070203030154/http://www.cis.rit.edu/fairchild/PDFs/PAP21.pdf
Munsell renotation data (Munsell Color Science Lab, RIT)
Conversions between the Munsell and sRGB colour systems (Paul Centore)
sRGB Centroids for the ISCC-NBS Colour System (Paul Centore)
Natural Colour System (NCS)
Natural Colour System (NCS)
NCS (Scandinavian Natural Colour System)
NCS Quick Course (NCS)
Swedish Natural Color System (Bruce MacEvoy)
See also Virtual Atlas (VCS Consulting) below.
Other Systems
Other Systems
Optical Society of America Uniform Color Scales (OSA-UCS)
See also Virtual Atlas (VCS Consulting) below.
Hungarian Coloroid Colour System
See also Virtual Atlas (VCS Consulting) below.
Online and Offline Programs
Online and Offline Programs
Virtual Atlas (VCS Consulting)
"This free web application (IE, Safari and Chrome compatible) provides virtual colour atlases for the Colorcurve, Coloroid, DIN-6164, Munsell, NCS, OSA-UCS, and Swiss Colour Atlas 2541 colour order systems and for the BS:5252, RAL-840HR, and RAL-841GL colour ranges. In addition, the application supports spectral curve calculation, colour difference calculation, colour comparison, and colour notation conversion. Each colour atlas can be viewed in a range of different planes, for example Munsell can be viewed as planes of constant hue, value, or chroma, and each plane can be magnified up to 800% displaying calculated intermediate colours not present in the actual atlas."
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