Color Terminology

Achromatic Color

A neutral color - black, gray or white. (See Chromatic.)

Additive Primary Colors

Light colors from which all colors can be made: red, green and blue (RGB). Adding all three in equal amounts produces white light. Adding the three colors in varying amounts produces all colors of the gamut. Adding two primary colors in equal amounts produces a subtractive primary. Read more about additive colors.

Black

The absence of all reflected light. When an object absorbs all light, it looks black.

Theoretically, when subtractive primaries (cyan, magenta and yellow) are combined at maximum intensity, the result should be black. This is true for color film. But the colors of printer ink are not as pure. Combining cyan, magenta and yellow printer ink results in a muddy brown. To correct the problem, printers use black ink for black.

Printer inks are abbreviated CMYK. A "K" is used for black to avoid confusion with blue.

Black Body Radiation

The light emitted by a black body. A black body absorbs all light which it receives. None is reflected and none passes through it. When a black body is cold, it appears black. Read about color temperature.

Blue

One of the three additive primary colors. It's wavelength is approximately 440 - 490 nanometers.

Brightness

Used in the HSB (hue, saturation, brightness) color model. Brightness is the degree to which a color appears to reflect light.

Chroma

The property of color which makes it appear to be strong in color (saturated). Pastel colors are low in chroma. A red apple is high in chroma. White, black and gray have no chroma.

Chroma is used in the LCH color model (lightness, chroma, hue) and the Munsell Color System.

Chromatic Color

All non-neutral colors, that is, all colors which are not black, gray or white. In the English language, the work "color" usually means a chromatic color.

Chromaticity

krohm uh tis' i tee

The quality of a color which is determined by its purity and dominant wavelength.

CIE

International Commission on Illumination. Commission internationale de l'éclairage (its French name.)

Established for the first time in 1931 a system of scientifically defining light colors or additive colors. It is the international organization which concerns itself with color and color management.

CIE XYZ

The color model developed by the CIE in 1931. It was the first model to mathematically define color. Others CIE models came later. It defines color in terms of the amount of each primary color that is needed to produce a color as the average person perceives it.

The CIE XYZ is different from other color models, like CMYK or RGB in that it allows us to unambiguously define color as it is perceived. The CMYK and RGB define amounts of color, not the actual color. Read more about CIE XYZ.

CIE LAB (CIE L* a* b*, CIELab, CIELAB)

Mathematically derived from the CIE XYZ. L* = lightness, a* = red-greenness, b* = yellow-blueness. These are synthetic primaries. Read more about CIE Lab.

CIE Standard Illuminants

The light source (illuminant) will affect our perception of a color due to the color temperature. Therefore, it is necessary to include the standard illuminant data in addition to any tristimulus values when describing a color.

The CIE established spectral data sets for different types of light sources which describe their spectral components. This data is used in place of any actual measurements of the light source.

CIE Standard Observer

People perceive color differently. In the 1920s, W. David Wright and John Guild conducted color experiments using a number of different people. The results of what these people perceived were tabulated. The CIE standard observer is the term given to the tabulated collective numerical values resulting from their experiments. Read more about the standard observer.

CIE Tristimulus Values

trī stim' yə ləs

The amount of each of the primary light colors (red, green, blue) needed to create a given color. See Tristimulus.

CIE xy Chromaticity Diagram

A 2-dimensional graph specifying coordinates for chromaticity. The brightness is constant.

CIE xyz Chromaticity Coordinates

The values used to plot the CIE xyY chromaticity diagram. This diagram visually represents the entire gamut of visible colors. The values were calculated from the CIE XYZ tristimulus values.

CMM

Color Matching Method. In order for a device to consistently produce a perceived color, it needs to be numerically adjusted. The adjustment will either be sent to or received from the device. This is done with software.

CMY

Cyan, magenta, yellow. These are the subtractive primary colors. CMY is a color space, a way of describing color.

CMYK

Cyan, magenta, yellow, black. "K" is used for black to avoid confusion with blue. Printers use these colors.

Color

A perception of what we see, based on how different wavelengths of light stimulate the color receptors or cones in the retina of our eyes.

Color Constancy

Our perception of surface colors will change as the light changes. Color constancy is the amount of stability of the color perception.

Color Management

In order for the color we perceive to be constant, signals sent to input, display and output devices need to be adjusted. Each device has a profile to reference color behavior to a known standard.

Color Matching Functions

Each wavelength of light needs to be matched to its relative amount of the three additive primaries. This is a numerical value and is usually based on the CIE Standard Observer.

Color Model

A way of defining colors mathematically. Usually based on relative values of the primary colors. Examples: RGB, CIELab, CMYK.

Color Separation

The colors used in a computer monitor (red, green and blue) are converted to cyan, magenta, yellow and black (CMYK) to enable a printer to reproduce them.

Color Space

A way of representing colors, usually three dimensional. Read more about color space.

Color Temperature

Our perception of a color actually changes with its temperature. Color temperature is the measurement of the color of white light, expressed in Kelvin. Read more about color temperature.

Color Wheel

A circle with the all colors of the visible spectrum going around it in a continuum. Complementary colors are opposite each other.

Colorant

The medium used to produce a color. This can be ink, pigment, toner, dye or phosphors.

Colorimeter

An instrument used to measure the relative intensities of red, green and blue light which is reflected or emitted (transmitted) through a color sample. Computer monitors use colorimeters.

ColorSync

A color management system which Apple Computer developed for the Macintosh operating system.

Complementary Colors

Colors which are opposite each other in a color model like a color wheel. When complementary colors are mixed together, they produce some shade of gray.

Cones

The part of the human eye which perceives color. There are three types of cones which are able to perceive either red, green or blue light. Read more about cones.

Cyan

A subtractive primary color. Cyan absorbs all red light and reflects green and blue. It wavelength is midway between blue and green and equals 485 nm. Used for printing.

Densitometer

An instrument used to measure optical density.

Density

See optical density.

Device Dependent

A description of a color space which depends on physical colorants and the physical properties of a device. Printers, for example, use the CMYK color space. Computer monitors use the RGB color space.

Device Independent

A description of a color space which uses primary colors as its basis and is not dependent on the properties of a physical device. Device-dependent color spaces can define an unambiguous definition of a color, based on human perception.

Dye

A colorant which is soluble, unlike pigment, which is insoluble. Dyes can produce brighter colors than pigments, but also are less stable and tend to fade over time.

Four Color Process

Depositing combinations of cyan, magenta, yellow and black on paper to produce a visible image. The colors are deposited as dots which are different shapes, sizes and angles in order to create an illusion of different colors.

Gamut

The full range of colors which can be perceived, produced or represented by a color model. Read more about color gamut.

Grassman's Laws

Laws developed by Hermann Grassmann which govern the results of additive color mixing.

Green

One of the three additive primary colors. It's wavelength is approximately 520 - 570 nanometers.

HiFi Printing

Adding additional, special ink colors to the cyan, magenta, yellow and black.

HSB Color Model

A color model based on the properties of hue (H), saturation (S) and brightness (B).

Hue

The color of an object or light source (red, orange, green, etc.)

Illuminant

A light source which has a known spectral distribution.

Intensity

How bright or dull, clear or muted a color is.

Kelvin (K)

Used to measure color temperature. The Kelvin scale starts at absolute zero which is equal to -273° Celsius.

LCH Color Model

Derived from CIELab. Instead of the rectangular coordinates, it uses lightness (L), chroma (C) and hue (H).

Light

The part of the electromagnetic spectrum which has a wavelength between 380 and 720, the part humans can see.

Lightness

The degree to which colors appear to reflect light. Used in the LCH color model.

LRV

Light Reflectance Value. The amount of visible light a surface reflects. Refers strictly to the lightness or darkness of a color.

This value usually appears on the back of a paint color strip. It ranges from 0% to 100% with 0% being absolute black and 100% being perfectly white. The LRV of 0% and 100% do not exist in reality. The blackest black on the LRV scale is 5%. The whitest white is about 85%.

Luminance

A measurement which describes the amount of light which passes through an area.

Luminosity

See brightness

Magenta

A subtractive primary color. Magenta absorbs all green light and reflects red and blue. It wavelength is midway between blue and green and around 550 nm. Magenta is used in printing.

Metamerism

Using the color gamut, a given color can be made by any number of combinations of the primary colors. Read more about metamerism.

Metamerism can also mean the phenomenon where a color looks different under different light sources due to color temperature. Read about color temperature.

Monochromatic

A type of color which consists of a single wavelength.

Munsell Color System

A three dimensional color space developed by Albert Munsell in the early part of the 20th century. It is based on the attributes of hue, value and chroma. Read more about the Munsell Color System.

Nanometer

A unit of measurement used to measure the wavelength of visible light. Abbreviated nm. There are one million nanometers in a millimeter.

Optical Density, OD

A measure of how much a material is able to absorb light. Darker materials have high optical density. Lighter materials have low. Expressed in units of OD.

Pigment

A colorant which is insoluble. (Dyes are soluble.) Pigments tend to fade less and be more permanent than dyes.

Pixel

Tiny dots which contain red, green and blue information in order to produce color on a monitor or scanner. They are similar to dots of ink on a piece of paper. The resolution of a monitor is expressed in terms of pixels per inch or ppi. (A printer's resolution is expressed in terms of dots per inch or dpi.)

Polarization

When the special orientation of the electromagnetic waves of light are not random, they are polarized. Read more about polarization.

Primaries

The components of a primary color in a color space or color model. The primaries may be actual primary colors as in CYMK and RGB or they may be mathematical values as in the CIE XYZ or CIELab.

Primary Color

A color which has a single frequency and cannot be made by any combination of other colors. All non-primary colors can be made by combining the primary colors.

Primary colors of light (additive) are red, green and blue (RGB). Primary colors of pigments or dyes (subtractive) are cyan, magenta and yellow (CMY).

Red

One of the three additive primary colors. It's wavelength is approximately 625 - 740 nanometers.

RGB

The additive primaries red, green and blue. See Additive Primaries.

RYB

The subtractive primaries red, yellow and blue. In the 18 th century, these three colors became the foundation of color theory.

Spatial Contrast

Two adjacent areas which have some visual difference, for example, black letters on a white page.

Saturation

The property of color which makes it appear to be strong in color. Pastel colors have low saturation. A red apple has high saturation. Also called chroma.

Spectral Data

Describing a color by specifying the amount of each wavelength the color contains. This is the most precise description of a color. Typically, 10 nanometer or 20 nanometer bands are used.

Spectral Light

A light color which is monochromatic, or nearly so.

Spectral Power Distribution

The amount of light at each wavelength produced by a light source.

Spectrophotometer

An instrument used to produce spectral data. It measures the amount of light a color reflects or transmits at each wavelength.

Spectrum

A representation of the spatial arrangement of electromagnetic energy, shown as a continuum of wavelength size.

Standard Illuminants

See CIE Standard Illuminants.

Standard Observer

See CIE Standard Observer.

Subtractive Primary Colors

Cyan, magenta and yellow, the primaries of pigments or dyes which create reflective colors. Cyan absorbs (subtracts) red light and reflects blue and green. Magenta absorbs (subtracts) green light and reflects blue and red. Yellow absorbs blue light and reflects red and green. Read more about subtractive primaries.

Tristimulus (Tri-stimulus)

trī stim' yə ləs

When describing color, there are three values used. Different color spaces use different values. The values are usually relative amounts of the three light source primary additive colors needed to produce a color. Read more about tristimulus.

Tristimulus Data

The three tristimulus values used to create or define a color. For example, in the RGB color space, Red 255, Green 0, Blue 0 would equal true red. Read more about tristimulus.

Visible Spectrum

The range of colors humans can see. We are able to see colors with wavelengths between 380 and 720 nanometers. The wavelengths in this range stimulate the cones (color receptors) in our retina. We see the shorter wavelengths as blue and violet. The longer wavelengths are seen as red and orange.

Yellow

A subtractive primary. Its wavelength is 570 - 580 nm. Yellow absorbs all wavelengths of blue light and reflects all red and green.