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Angle of Incidence
The angle at which a beam of light strikes the surface of an object compared to the perpendicular to the object surface.
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Attribute
Distinguishing characteristic of a sensation, perception or mode of appearance. Colors are often described as their attributes of hue, saturation or chroma, and lightness.
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Artificial Daylight
Term loosely applied to light sources, frequently equipped with filters, that try to reproduce the color and spectral distribution of daylight. A more specific definition of the light source is preferred.
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Appearance
Manifestation of the nature of objects and materials through visual attributes such as size, shape, color, texture, glossiness, transparency, opacity, etc.
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Apparent Color Temperature
The color appearance of a light source related to the absolute color temperature of a black body radiator having the same color
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a*
Red-green coordinate in CIE L*a*b* color space. A positive a* value indicates redness and a negative a* value indicates greenness
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Angle of Reflection
The angle at which a beam of light is reflected from the surface of an object compared to the perpendicular to the object surface.
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Additive Primaries
Red, green, and blue light. When all three additive primaries are combined at 100% intensity, white light is produced. When these three are combined at varying intensities, a gamut of different colors is produced. Combining two primaries at 100% produces a subtractive primary, either cyan, magenta, or yellow 100% red + 100% green = yellow; 100% red + 100% blue = magenta; 100% green + 100% blue = cyan. See Subtractive Primaries
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Additive Color Mixture
Mixing of the three primary color lights (red, green and blue) to obtain colors. For example, combining green and red creates yellow, red and blue creates magenta, and blue and green creates cyan.
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Adaptation
The ability of the eye to adjust to different light sources or light levels. This allows the visual system to adjust its sensitivity to different lighting conditions.
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Achromatic Color
A neutral color (white, gray or black) that has no chroma and no hue.
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Absorbance
Absorbance is ?light-stopping ability.? The higher the value, the more light the sample absorbs. Values typically range from 0 to 3.0. Mathematically, absorbance is calculated A = log10(l/T) where T is transmittance, expressed as a decimal from 0 to 1 (for example, 0.5R is 50%R). This is the same equation used to calculate density in graphic arts and photography applications.
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Absorb/Absorption
Dissipation of the energy of electromagnetic waves into other forms as a result of its interaction with matter; a decrease in directional transmittance of incident radiation, resulting in a modification or conversion of the absorbed energy.
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Absolute White
In theory, a material that reflects all light energy at every visible wavelength. In practice, a solid white with a known spectral reflectance data that is used as the reference white for all measurements of absolute reflectance. When calibrating a spectrophotometer, often a white ceramic plaque is measured and used as the absolute white reference.
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Angle of View
The angle at which a sample is viewed compared to the perpendicular of the surface
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Beer?s Law
Describes the mathematical relationship between the absorption of light energy relative to the concentration of a dye or pigment.
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Brightness
The attribute of visual perception in accordance with which an area appears to emit or reflect more or less light (this attribute of color is used in the color model HSB ? Hue, Saturation, Brightness). Both the saturation and lightness of product color. See Lightness.
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Black
The absence of all reflected light; the color that is produced when an object absorbs all wavelengths from the light source.
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b*
Yellow-blue coordinate in CIE L*a*b* color space. A positive b* value indicates yellowness and a negative b* value indicates blueness.
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Black Body (Planckian) Locus
The set of points on a chromaticity diagram representing the colors of perfect radiators having various color temperatures.
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Black Body Radiator
In theory, an object that absorbs all energy that comes into contact with it.
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Color Model
A color measurement scale or system that numerically specifies the perceived attributes of color. Used in computer graphics applications and by color measurement instruments.
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Color Wheel
The visible spectrum?s continuum of colors arranged into a circle, where complementary colors such as red and green are located directly across from each other.
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Color Temperature
A measurement of the color of light radiated by an object while it is being heated. This measurement is expressed in terms of absolute scale, or degrees Kelvin. Lower Kelvin in temperatures such as 2400?C are red; higher temperatures such as 9300?C arc blue Neutral temperature is gray, at 6504?K.
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Color Specification
Tristimulus values, chromaticity coordinates and luminance value, or other color-scale values, used to designate a color numerically in a specified color system.
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Color Space
In general, a collection of systematically ordered color, or a system of ordering colors. A color space can be defined by a physical collection of samples or by a mathematical system. In the context of instrumental color measurement, a three-dimensional volume defined by a set of equations, in which any color may be located precisely based on instrumental measurement. For example, the three-dimensional volume described by the CIELab system is called CIELab color space (CIELab is an opponent color scale).
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Color Separation
The conversion of the red, green, and blue color information used in a computer into cyan, magenta, yellow, and black channels that are used to make printing plates.
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Color Order Systems
Systems used to describe an orderly three0dimensional arrangement of colors. Three bases can be used for ordering colors: (1) an appearance bases (i.e., a psychological basis) in terms of hue, saturation and lightness; an example is the Munsell System; (2) an orderly additive color mixture basis (i.e., a psychophysical basis); examples are the CIE System and the Ostwald System; and (3) an orderly subtractive color mixture basis; an example is the Plochere Color System based on an orderly mixture of inks.
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Color Measurement Scale
A system of specifying numerically the perceived attributes of color
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Color Matching Functions
Relative amounts of three additive primaries required to match each wavelength of light. The term is generally used to refer to the CIE Standard Observer color matching functions designated. See CIE Standard Observer.
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Color Management
Matching colors between an original image, scanner, monitor, color printer and final press sheet.
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Color Difference, Visual
The difference between two colors that the human eye sees. It is usually described in qualitative terms such as lighter, darker, redder, greener, bluer, yellower, paler, more saturated, and so forth.
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Control Limits
The amount of acceptable variation in press capabilities over the course of a press run.
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Color Rendering Index
Measure of the amount of color change that objects exhibit when illuminated by a light source as compared with the color of those same objects when illuminated by a reference source of comparable color temperature.
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Colorant Mixture
A mixture of dyes or pigments.
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Colorants
Materials used to create colors?dyes, pigments, tuners, phosphors.
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Colorimeter
An optical measurement instrument that responds to color in a manner similar to the human eye?by filtering reflected light into its dominant regions of red, green, and blue.
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Colorimetric
Of or relating to values giving the amounts of three colored lights or receptors?red, green, and blue.
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Colorist
A person skilled in the art of color matching (colorant formulation) and knowledgeable concerning the behavior of colorants in a particular material; a tinter (q.v.) (in the American usage) or a shader. The word colorist is of European origin.
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ColorSync
Built-in color management architecture for Apple Macintosh computers. Third-parts vendors utilize the ColorSync framework to provide device calibration, device characterization, and device profile-building methods.
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Commission Internationale de l?Eclairage
The Commission is devoted to standardization in illumination and related areas that include color. The CIE operates through a series of committees.
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Complements
Two colors that create neutral grey when combined. On a color wheel, complements are directly opposite from each other blue/yellow, red/green, and so on.
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Color Difference, Numerical
The difference between color coordinate values for two different samples. Numerical color difference quantifies the difference between two colors.
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Contrast
The level of variation between light and dark areas in an image.
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Color Tolerance
An acceptable color difference between a standard (master) and a trial (batch)
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Correlated Color Temperature
The temperature in degrees Kelvin of a point on a black body locus which most closely resembles the light source.
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Cyan
One of the process ink colors for printing. Pure cyan is the ?redless? color; it absorbs all red wavelengths of light and reflects all blue and green wavelengths.
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Conditional Match
A set of samples which appear to match under a limited set of conditions such as light source or viewing angle.
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CIE Standard Illuminants
Known spectral data established by the CIE for four different types of light sources. When rising tristimulus data to describe a color, the illuminant must also be defined. These standard illuminants are used in place of actual measurements of the light source.
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Color Difference Equations
Mathematical equations that calculate the magnitude of difference between two colors. Some equations convert CIE coordinates into more uniform differences that more closely simulate usual perception of color difference.
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C*
Chromaticity coordinate in CIE L*C*h color space. A chroma of 0 (zero) indicates a perfectly neutral color. A large C* value indicates a more chromatic or saturated color.
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Calibration
To check, adjust, or systematically standardize the performance of a device
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Chroma
The attribute of visual perception in accordance with which au area appears saturated with a particular color or hue-for example, a red apple is high in chroma; pastel colors arc low in chroma; black, white, and gray have no chroma (this attribute of color is used in the color model L*C*H?Lightness, Chroma, Hue) Also referred to as Saturation.
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Chromatic
Having color (hue); not neutral (black, white or gray).
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Chromaticity Diagram
In practical terms, a two-dimensional graph on which a color may be plotted according to its hue and chroma. The third dimension of this graph is the luminance factor, or lightness, which is independent of hue or chroma. The location of a point on this graph indicates roughly what color it is (red, green, blue, purple, and so forth) and how saturated it appears. This information must be interpreted with caution, since the coordinates of neutral colors differ with each illuminant. The coordinates can rarely be interpreted with appearance unless the illuminant is specified. A plot of all colors has a characteristic horseshoe shape.
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Chromaticity, Chromaticity Coordinates
Dimensions of a color stimulus expressed in terms of hue and saturation, or redness-greenness and yellowness-blueness, excluding the luminous intensity. Generally expressed as a point in a plane of constant luminance. See CIE xy Chromaticity Diagram.
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CIE (Commission Internationale de I?Eclairage)
A French name that translates to International Commission on Illumination, the main international organization concerned with color and color measurement.
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Color
One aspect of appearance; a stimulus based on visual response to light, consisting of the three dimensions of hue, saturation, and lightness.
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CIE Luminosity Function (Y)
A plot of the relative magnitude of the visual response as a function of wavelength from about 380 to 790 nm, adopted by CIE in 1931.
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CIE Standard Observer
A hypothetical observer having the tristimulus color mixture data recommended in 1931 by the CIE for a 2? viewing angle. A supplementary observer for a larger angle of 10? was adopted in 1964. If not specified, the 2? Standard Observer should be assumed. If the field of view is larger than 4?, the 10? Standard Observer should be used.
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CIE Tristimulus Values
Amounts of the three components necessary in a three-color additive mixture required for matching a color in the CIE System, they are designated as X, Y, and Z. The illuminant and standard observer color matching functions used must be designated; if they are not, the assumption is made that the values are for the 1931 GIL 2? Standard Observer and Illuminant C.
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CIE xy Chromaticity Diagram
A two-dimensional graph of the chromaticity coordinates, x as the abscissa and as the ordinate, which shows the spectrum locus (chromaticity coordinates of monochromatic light, 380?770nm). It has mans useful properties for comparing colors of both luminous and non-luminous materials.
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Color Aptitude
The ability to work with and understand color; includes both inherited skills and work experience.
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Color correction
A photographic or electronic process that is used to compensate for the unwanted absorptions of process inks and also the deficiencies of the color separation process. A color correction can also refer to any color change requested by the client.
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CIE Chromaticity Coordinates
x and y values that specify the location of a color within the CIE chromaticity diagram.
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Color Attribute
Three-dimensional characteristic of the appearance of an object. One dimension usually defines the lightness, the other two together define color
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CIE
The abbreviation for the French title of the International Commission on Illumination, Commission Internationale de l?Eclairage. The Commission is devoted to standardization in illumination and related areas that include color. The CIE operates through a series of committees.
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CMY
The subtractive primaries cyan, magenta, and yellow. See Subtractive Primaries.
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CMC
A color difference formula based on the CIELCh (opponent color scale) color space, in which equivalent total color difference values represent equivalent visual differences, regardless of the color
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CMC (Color Measurement Committee)
Of the Society of Dyes and Colorists in Great Britain. Developed a more logical, ellipse based equation for computing ?E values as an alternative to the spherical regions of the CIELAB color space.
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CIELCh
A uniform (opponent color scale) color space in which colors are located within a three-dimensional polar coordinate system; the three dimensions are lightness (L*), chroma (C*), and hue angle (h). CIELCh is part of the current CIE recommendations. To pronounce CIELCh, just say the letters.
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CIELab
A uniform (opponent color scale) color space in which colors are located within a three-dimensional rectangular coordinate system; the three dimensions are lightness (L*), redness greenness (a*) and yellowness blueness (b*). CIELab is part of the current CIE recommendations. A uniform color space utilizing an Adams Nickerson cube root formula, adopted by the CIE in 1976 for use in the measurement of small color differences. Pronounced ?see-lab? and also referred to as L*a*b* (pronounced, ?el-star?, ?ay-star?, ?bee-star?).
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CIELAB (or CIE L*a*b*, CIE Lab)
Color space in which values L*, a*, and b* are plotted at right angles to one another to form a three dimensional coordinate system. Equal distances in the space approximately represent equal color differences. Value L* represents Lightness; value a* represents the Redness/Greenness axis; and value b* represents the yellowness/blueness axis. CIE All is a popular color space for use in measuring reflective and transmissive objects.
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CIE94/CIE2000
The CIE94/CIE2000 tolerancing method utilizes three-dimensional ellipsoids as 'containers' for color acceptance. They are conceptually similar to CMC2, but lacks some of the hue and lightness adjustments. It is expected that CIE94/C1E2000 will evolve over the next few years as additional studies are performed
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CIELUV (or CIE L*u*v*)
Color space in which values L*, a*, and b* are plotted at right angles to one another to form a three dimensional coordinate system. Equal distances in the space approximately represent equal color differences. Value L* represents Lightness; value a* represents the Redness/Greenness axis; and value b* represents the yellowness/blueness axis. CIE All is a popular color space for use in measuring reflective and transmissive objects.
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Color Constancy
Relative independence of perceived object color to changes in color of the light source.
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Diffused Light
Nondirectional or scattered light.
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Density
Refers to a computed number representing the ability of a transmissive material to block light, or the ability of a reflective surface to absorb light. The more light blocked or absorbed, the higher the density.
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Device Profile
Device specific color information that is a characterization of a device?s color rendering and reproduction capabilities. Monitor profiles, scanner profiles, and printer profiles are utilized in a color management system such as Apple ColorSync to help the devices communicate color information with each other. Profiles are created by calibration and/or characterization method.
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Device-Dependent
Describes a color space that can he defined only by using information on the color-rendering capabilities of a specific device. For example, the RGB color space must be generated by a monitor, a device which has specific capabilities and limitations for achieving its gamut of colors. In addition, all monitors have different capabilities and limitations, as do different scanners, printers, and printing presses.
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Device-Independent
Describes a color space that can be defined using the full gamut of human vision, as defined by a standard observer, independent of the color-rendering capabilities of any specific device.
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Dialog Box
A window that appears temporarily to request information. Many dialog boxes have options you must choose before Microsoft* Windows* can carry out a command.
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Diffuse Transmission
Diffusion of light energy being transmitted through a sample and subject to the laws of refraction.
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Dye
A soluble colorant; as opposed to pigment, which is insoluble.
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Dynamic Range
An instruments range of measurable values, from the lowest amount it can detect to the highest amount it can handle.
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Delta Transmittance
The difference in transmittance values, at each wavelength, between trials and the standard. Positive delta transmittance means the trial transmits more light than the standard. Negative delta transmittance means the trial transmits less light than the standard.
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Diffuse Reflection
Reflection in which light energy is scattered in many directions by diffusion at or below the surface.
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D65
The CIE Standard Illuminant that represents a color temperature of 6504?K.
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Densitometer
A sensitive, photoelectric instrument that measures the density of images or colors.
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Delta Value
A conversational term for ?delta color coordinate? sometimes, the word ?deltas? is used. For example, in CIELab calculations, Delta L*, Delta a* and Delta b* are all called ?CIELab delta values? or ?CIELab deltas.? This term is used to facilitate spoken communication.
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D50
The CE Standard Illuminant that represents a color temperature of 5000? K. This is the color temperature that is most widely used in graphic arts industry viewing booths. See Illuminants D.
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Delta (?)
A symbol used to indicate deviation or difference.
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Delta Absorbance
The difference in absorbance values, at each wavelength, between trials and the standard. Positive delta absorbance means the trial absorbs more light than the standard. Negative delta absorbance means the trial absorbs less light than the standard.
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Delta E, ?E, or DE
The generic name for total color difference, and is used to indicate total color difference for all uniform color spaces. Total color difference (Delta E) is a single number that expresses the magnitude (size, degree, amount) of difference between two colors. The value tells nothing about the nature of the color difference.
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Delta Error (?E)
In color tolerancing, the symbol ?E is used to express Delta Error, the total color difference computed using a color difference equation. The color difference is generally calculated as the square root of the combined squares of the chromaticity differences, ?a* and ?b*, and the Lightness difference, ?L. See CIE94.
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Delta K/S
The difference in K/S values, at each wavelength, between trials and the standard. Positive delta K/S means the trial has a higher absorption-to-scattering ratio than the standard. Negative delta K/S means the trial has a lower absorption-to-scattering ratio than the standard.
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Delta Reflectance
The difference in reflectance values, at each wavelength, between trials and the standard. Positive delta reflectance means the trial reflects more light than the standard. Negative delta reflectance means the trial reflects less light than the standard.
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Electromagnetic Spectrum
The massive hand of electromagnetic waves that pass through the air in different sizes, as measured by wavelength. Different wavelengths have different properties, but most are invisible?and some completely undetectable?to human beings. Only wavelengths that are between 380 and 720 nanometers in size are visible, producing light. Invisible waves outside the visible spectrum include gamma rays x-rays, microwaves, and radio waves.
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Ellipsoid
A solid whose plane sections are all ellipses (closed curves produced when a cone is cut obliquely to its axis by a plane).
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Emissive Object
An object that emits light. Usually some sort of chemical reaction, such as the burning gasses of the sun or the heated filament of a light bulb.
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Fluorescent Whitening Agent (FWA)
A fluorescent dye or pigment that absorbs UV energy and re-emits the energy at a higher wavelength as visible light (violet blue) thereby causing a white appearance.
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FMC-2
A color difference equation developed by Friele, MacAdam and Chickering. The equation was derived from the results of an extensive visual assessment experiment. For most colors, a total color difference (Delta E) value of 1.0 represents a just noticeable difference.
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Four-Color Process
Depositing eliminations of the subtractive primaries cyan, magenta, yellow, and black on paper to achieve dots of different sizes, shapes, and angles to create the illusion of different colors. See CMY, Subtractive Primaries.
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Fluorescent Lamp
A glass tube filled with mercury gas and coated on its inner surface with phosphors. When the gas is charged with an electrical current, radiation is produced which in turn energizes the phosphors, causing the phosphors to glow.
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Fluorescence
Process by which energy, usually UV, is absorbed by certain chemicals or materials and re-emitted at other, usually longer, wavelengths.
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Flair
The change in hue of a sample when the light source is changed; the opposite of color constancy.
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Foot Candle
The quantity of light at a point on a plane surface one foot from and perpendicular to a standard candle.
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Fluorescent Lamp
A low pressure mercury electric-discharge lamp in which a fluorescing coating (phosphor) transforms some ultraviolet energy generated by the discharge into visible light.
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Geometric Metamerism
The property exhibited by a pair of samples (usually highly textured) that appear to match at one illumination and viewing angle, but no longer match when either the angle of illumination or viewing angle is changed.
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Grayscale
An achromatic scale ranging from black through a series of successively lighter grays to white. Such a series may be made up of steps that appear to be equally distant from one another, or it may be arranged according to some other criteria such as a geometric progression based on lightness. Such scales may be used to describe the relative amount of difference between two similar colors.
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Goniospectrophotometer
An instrument used to measure a spectrophotometric curve at various angles of incidence and reflectance. The angles of incidence and reflectance can be changed or are offered at fixed intervals (e.g., 15, 45, 75, 110 degrees).
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Goniochromatism
The phenomenon where the color of a material changes as the angle of illumination or viewing is changed.
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Goniochromatic
Adjective used to describe a colored material that exhibits goniochromatism.
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Gloss
An additional parameter to consider when determining a color standard, along with hue, value, chroma, the texture of a material and whether the material has metallic or pearlescent qualities. Gloss is an additional tolerance that may be specified in the Munsell Color Tolerance Set. The general rule of evaluating the gloss of a color sample is the higher the gloss unit, the darker the color sample will appear. Conversely, the lower, the gloss unit, the lighter a sample will appear.
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Geometric Attributes
The characteristics associated with light distribution from an object including gloss, haze, texture, shape, viewing angle and surround.
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Gamut
the range of different colors that can be interpreted by a color model or generated by a specific device.
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Gamut Mapping
Converting the coordinates of two or more color spaces into a common color space. Often results in tonal range compression. See Gamut Compression.
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Gamut Compression
Or tonal range compression. The color space coordinates of a color space with a larger gamut are reduced to accommodate the smaller gamut of a destination color space. For example, the gamut of photographic film is compressed for representation in the smaller CMYK gamut used for four-color process printing. See Gamut.
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Glossmeter
An instrument used to measure the amount of gloss (a term used to describe the relative amount of mirror-like (specular) reflection from the surface of a sample). These instruments measure the light reflected at select specular angles, such as 20 degrees from the perpendicular, 45, 60, 75, and 85 degrees. Results obtained are very dependent on instrument design, calibration technique used, types of samples, and so forth.
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Hue
the basic color of an object, such as ?red,? ?green,? ?purple,? etc. Refined by its angular position in a cylindrical color space, or on a Color Wheel.
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Haze
The scattering of light by a specimen responsible for the apparent reduction of contrast of objects viewed through it or contrast of objects viewed by reflection at the surface.
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HiFi Printing
Process printing that expands the conventional four-color process gamut using additional, special ink colors.
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Hue
The attribute of color used in the Munsell Color System by which we distinguish red from green, blue from yellow and so forth.
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Illuminant TL83
Mathematical representation of commercial, rare earth phosphor, narrow band fluorescent used in Europe and the Pacific Rim. Color temperature of 3000K. Uses include metamerism testing. Simulates typical office or store lighting in Europe and the Pacific Rim.
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ICM
Built-in color management architecture for computers running the Window?s operating system. Third-party vendors utilize the ICM framework to provide device calibration, device characterization, and device profile building methods.
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IT8
Series of test targets and tools for color characterization established by? ANSI (American National Standards Institute) Committee IT8 for Digital Data Exchange Standards. Different IT8 targets are used to characterize different devices such as scanners and printers.
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Intensity
Saturation or reflective energy as related to visible wavelengths of light. Reflectance of wavelengths at high intensity generates high saturation, or chroma.
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Integrating Sphere
A sphere coated inside with a highly reflective, diffuse material and used to collect for measurement the light reflected or transmitted by a specimen.
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Incandescent
A lamp in which light is produced by a filament heated by an electric current so that it glows.
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Illuminants F (CIE)
GE Standard Illuminant for fluorescent illumination. P2 represents a cool white fluorescent lamp (4200 KI, P7 represents a broad-hand daylight fluorescent lamp (6500 K), and Ft I represents a narrow-hand white fluorescent lamp (4000 K).
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Illuminants D (CIE)
CIE Standard Illuminants for daylight, based on actual spectral measurements of daylight. D65 with a correlated color temperature of 6504?K is most commonly used. Others include D50, D55, and D75.
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Illuminant
An illuminant is a mathematical representation of a theoretical real light source, used for calculating tristimulus values from a spectrophotometric measurement. The numbers represent relative power of the theoretical source at each point in the visible spectrum. The relative power distribution of a real source could be used for calculation, but real sources are difficult to standardize.
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Illuminant U30
Mathematical representation of commercial, rare earth phosphor, narrow band fluorescent. Color temperature 3000K. Uses include metamerism testing. Simulates typical store lighting for Sears. USA equivalent of TL83.
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Illuminant TL84
Mathematical representation of commercial, rare earth phosphor, narrow band fluorescent used in Europe and the Pacific Rim. Color temperature of 4100K. Uses include metamerism testing. Simulates typical office or store lighting in Europe and the Pacific Rim.
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Illuminant SPL (HOR)
Mathematical representation of Tungsten Halogen as found in SpectraLight (Horizon). Color temperature of 2300K. Uses include metamerism testing. Simulates early morning sunrise or late afternoon sunset.
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Illuminant SPL (D75)
Mathematical representation of GretagMacheth-patented, Filtered Tungsten Halogen as found in SpectraLight (Daylight). Color temperature of 7500K. Uses include critical evaluation of color, metamerism testing, and visual evaluation of opaque materials as outlined by ASTM D1729. Simulates north sky daylight.
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Illuminant C
Mathematical representation of filtered tungsten halogen (daylight). Color Temperature of 6770K. Uses include metamerism testing. Simulates the CIE average daylight.
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ICC (International Color Consortium)
A group of hardware and software companies dedicated to the development of a specification that is OS independent and provides the digital imaging, printing and related industries with a data format for defining the color and reproduction characteristics of devices and their related media. http://www.color.org/
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Illuminant A (CIE)
CIE Standard Illuminant for incandescent illumination, yellow-orange in color, with a correlated color temperature of 2856?K.
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Illuminant TL85
Mathematical representation of commercial, rare earth phosphor, narrow band fluorescent used in Europe and the Pacific Rim. Color temperature of 5000K. Uses include metamerism testing. Simulates typical office or store lighting in Europe and the Pacific Rim.
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Illuminant C (CIE)
CIE Standard Illuminant for tungsten illumination that simulates average daylight, bluish in color, with a correlated color temperature of 6774?K.
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Illuminant SPL (D65)
Mathematical representation of GretagMacbeth-patented Filtered Tungsten Halogen as found in SpectraLight (Daylight). Color temperature of 6500K. Uses include critical evaluation of color, metamerism testing, providing visual correlation with spectrophotometric instrumental readings, conformance with European and Japanese standards, and agreement with the current Automotive standard. Stimulates average north sky daylight.
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Illuminant CWF-2 (F2)
mathematical representation of commercial, wide band fluorescent used in the USA (Cool White Fluorescent). Color temperature of 4150K. Uses include metamerism testing. Simulates typical office or store lighting in the USA.
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Illuminant D50
Mathematical representation of noon sky daylight. Color temperature of
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Illuminant D55
Mathematical representation of noon sky daylight .Color temperature of 5500K. Uses include metamerism testing. Simulates the CIE average noon sky daylight.
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Illuminant D65
Mathematical representation of average north sky daylight. Color temperature of 6500K. Uses include general evaluation of color, metamerism testing, providing visual correlation with spectrophotometric instrumental readings, and conformance with European and Japanese standards. Simulates average north sky daylight.
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Illuminant D75
Mathematical representation of north sky daylight. Color temperature of 7500K. Uses include general evaluation of color, metamerism testing, and visual evaluation of opaque materials as outlined by ASTM Dl729. Simulates north sky daylight.
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Illuminant DLF-7
Mathematical representation of commercial, wide band fluorescent used in the USA (Deluxe). Color temperature of 6500K. Uses include metamerism testing.
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Illuminant NBF-11
Mathematical representation of commercial, narrow band fluorescent used in the USA. Color temperature of 4000K. Uses include metamerism testing. USA equivalent to TL84.
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Illuminant A
Mathematical representation of tungsten halogen (incandescent). Color temperature of 2856K. Uses include metamerism testing. Simulates typical home or store accent lighting.
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K/S (?K over S?)
The ratio of the absorption coefficient (K) versus the scattering coefficient (S) for a reflectance measurement. The ratio is derived mathematically from the reflectance measurement as follows
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Kelvin (K)
Unit of measurement for color temperature. The Kelvin scale starts from absolute zero, which is -273? Celsius.
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Kubelka-Munk
Phenomenological turbid-medium theory relating the reflectance and transmittance of scattering and absorbing materials to optical constants. Theory includes variables where K represents the absorption coefficient and S the scattering coefficient for the concentrations of colorants. Also known as K over S data, this relationship is the basis of virtually all computer color matching calculations.
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Lightness
The attribute of visual perception in accordance with which an area appears to emit or reflect more or less light. Also refers to the perception by which white objects are distinguished from gray objects and light from dark colored objects
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L*C*H
A color space that is similar to CIELAB, except uses cylindrical coordinates of lightness, chroma, and hue angle instead of rectangular coordinates.
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Luster
The appearance characteristic of a surface that reflects more in some directions than it does in other directions but not of such gloss as to form clear mirror images.
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Log K/S
The base 10 logarithm of K/S values at each wavelength. A spectral plot (log K/S versus wavelength) shows that vertical distances between two curves (samples) are virtually the same for most wavelengths. Therefore, the vertical position of the curve relates directly to the colorant concentration. Also, the shape of the curve is almost independent of colorant concentration.
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Log Absorbance
The base 10 logarithm of absorbance values at each wavelength. A spectral plot (log absorbance versus wavelength) shows that vertical distances between two curves (samples) are virtually the same for all wavelengths. Therefore, the vertical position of the curve relates directly to the colorant concentration or sample thickness. Also, the shape of the curve is independent of colorant concentration or sample thickness.
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Light Source
That element in an instrument or in the visual observing situation that furnishes radiant energy in the form of light.
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Lab (Hunter Lab)
A uniform (opponent color scale) color space in which colors are located within a three-dimensional rectangular coordinate system; the three dimensions are lightness (L), redness greenness (a), and yellowness blueness (b).
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Lambert?s Law
The flux reflected per unit solid is proportional to the cosine of the angle measured from the normal (perpendicular) to the surface.
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Light
Electromagnetic radiation that has a wavelength in the range from 380 (violet) to about 770 (red) nanometers (nm), and can be perceived by the normal, unaided human eye.
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Monitor RGB
Same as RGB; monitor RGB simply refers specifically to the color space that can be achieved by a particular monitor using combinations of red, green, and blue light.
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Munsell Color Charts
A three dimensional color system developed by Albert Munsell that is based on the attributes Munsell Hue, Munsell Value, and Munsell Chroma.
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Metamerism
A phenomenon exhibited by a pair of colors which match under one or more sets of real or calculated conditions and not match when these conditions are changed.
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Metamerism, Metameric Pair
The phenomenon where two colors appear to match under one light source, yet do not match under a different light source. Two such colors are called a metameric pair.
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Metameric Pair
A pair of colors which match when viewed in a described way, hut no longer match if the viewing conditions change.
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Match
Generally, two colors match if they appear to be the same (have the same color coordinate values). The word ?match? is often used to indicate a spectral match, which means the two colors will appear to be the same (have the color coordinates) regardless of illuminant or observer.
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Magenta
One of the process ink colors for printing. Pure magenta is the ?greenless? color; it absorbs all wavelengths of green from light and reflects all red and blue wavelengths.
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MacAdam Unit
A unit of color difference as calculated by the FMC-2 equation. One MacAdam unit corresponds to a just-noticeable difference, based on experimental results.
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MacAdam Ellipses
Ellipsoids plotted on the chromaticity diagram that correspond to a just-noticeable difference from the color represented by the center of the ellipsoid. The size and shape of the ellipsoids depend on their location on the chromacity diagram.
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Matte Finish
A surface which displays no gloss when observed at any angle; a highly diffusely reflecting surface.
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Normal Color Vision
Vision of a normal observer who exhibits no symptoms of anomalous or defective color response.
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Narrow Band Fluorescent
Generic term for fluorescent lamp products such as Ultralume and TL84 that produce narrow bands of visible light energy as a function of their phosphor blend.
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Nonmetameric Match
A pair of colors which appear to be identical to all observers under all conditions of illumination and viewing; an unconditional match.
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Nanometer (nm)
Unit of length equal to 10-9 meter, or one millionth of a milli-meter. Wavelengths are measured in nanometers.
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Overprint
On a press sheet color bar, overprints are color patches where two process inks have been printed, one atop the other. Checking the density of these patches allows press operators to determine trap value. The term Overprint also applies to any object printed on top of other colors.
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Opponent Color Theory
Theory explaining conceptually how the human visual system (eye and brain combination) perceives color. To the human visual system, red and green are opposites, and yellow and blue are opposites. To a human observer this means that something that is red has no green in it (it may also be blue or yellow), while something that is yellow has no blue in it (it may also be red or green). Something that is neither red nor green is neutral with respect to redness greenness. Something that is neither yellow nor blue is neutral with respect to yellowness blueness. If a color is neutral with respect to both, it is a ?colorless? neutral (such as a black, gray or white). This theory is the basis for most uniform color spaces (especially CIELab, CIELCh, and Lab).
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Observer Metamerism
A pair of colors which match when viewed by one observer, but no longer match when viewed by another observer.
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Opaque
Term used to describe complete opacity, i.e., the degree to which a specimen obscures the substrate beneath it, opposite of transparent
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Photoreceptor
The cone- and rod-shaped neurons that cover the retina of the eye. Photoreceptors are excited by visible wavelengths, then send signals to the brain here the sensation of color is perceived.
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Process Control
Using densitometric and colorimetric measurement data from press sheet color bars to monitor press performance throughout the press run. Data is analyzed in relation to established control limits. See Control Limits.
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Prism
triangular shaped glass or other transparent material. When light is passed through a prism, its wavelengths refract into a rainbow of colors. This demonstrates that light is composed of color, and indicates the arrangement of colors in the visible spectrum. See Visible Spectrum.
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Primary Colors
The dominant regions of the visible spectrum red, green, and blue; and their opposite .
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Psychophysical
A term used to describe the area of color science which deals with the relationship between physical description and the sensors perception resulting from them.
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Photopic Vision
Adjective used to describe vision mediated by the cone receptors in the retina of the eye, which give rise to the sensation of color occurring at high and medium levels of luminance.
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Photoelectric
Pertaining to the electrical effects of light or other radiation?for example, emission of electrons.
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Photochromism
A reversible change in color of a specimen due to exposure to light.
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Phosphors
Materials that emit light when irradiated by cathode rays, or when placed in an electric field. The quantity of visible light is proportional to the amount of excitation energy present.
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Pixel
A tiny picture element that contains red, green, and blue information for color rendering on a monitor or a scanner. When generating colors, pixels are similar to dots of ink on paper. A monitor resolution description in terms of pixels-per-inch (ppi) is similar to a printer resolution description in terms of dots-per-inch (dpi).
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Pigment
An insoluble colorant; as opposed to a dye, which is soluble.
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Reflective Object
A solid object that returns some or all of the wavelengths of light that strike its surface. A reflective object that returns 100% of all light is called a perfect diffuser-a perfectly white surface.
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RGB
The additive primaries red, green, and blue. See Additive Primaries.
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Reflection
The process by which incident light leaves a surface or medium from the side on which it is incident.
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Reflectance
The percentage of light that is reflected from an object. Spectrophotometers measure an object?s reflectance at various intervals along the visible spectrum to determine the object color?s spectral curve. See Spectral Curve, Spectral Data.
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Radiant Energy
A form of energy consisting of the electromagnetic spectrum, which travels at 299,792 kilometers/second (188,206 miles/second) through a vacuum and more slowly in denser media (air, water, glass, etc.). The Nature of radiant energy is described by its wavelength of frequency, although it also behaves as distinct quanta. The various types of energy may be transformed into other forms of energy (electrical, chemical, mechanical, atomic, thermal, radiant), but the energy itself cannot be destroyed.
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Subtractive Primaries
Cyan, Magenta, and Yellow. Theoretically, when all three subtractive primaries are combined at 100% on white paper, black is produced. When these three are combined at varying intensities, a gamut of different colors is produced. Combining two primaries at 100% produces an additive primary, either red, green, or blue
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Specular Component Included (SCI)
Measurement of the total reflectance from a surface, including the diffuse and specular reflectance.
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Subtractive Color Mixture
Colorant mixture which must take into account both the absorption and scattering of two or more of the individual pigments used in the mixture.
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Standard
An established, approved reference against which instrument measurements of samples are evaluated.
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Standard Observer (1931, 2 Degree Observer)
The 2 degree visual field observer is the standard observer recommended by the Commission International de l?Eclairage (CIE) in 1931. This is based on the results of a color matching experiment that used a 2 degree field of view.
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Standard llluminant
The relative energy emitted by a real or imaginary light source that is mathematically defined at each wavelength across its spectral distribution.
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Specular
Having the qualities of a speculum or mirror; a smooth reflecting surface.
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Specular Reflection
Reflectance of a beam of radiant energy at an angle equal but opposite to the incident angle; the mirror- like reflectance.
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Specular Gloss
Relative luminous fractional reflectance from a surface in the mirror or specular direction.
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Supplemental Observer (1964, 10 Degree Observer)
The 10 degree visual field observer is the supplementary observer adopted by the Commission International de l?Eclairage (CIE) in 1964. This is based on the results of a color matching experiment that used a 10 degree field of view.
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Scotopic Vision
Vision mediated by rods alone at very low levels of illumination; night vision.
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Specular Component Excluded (SCE)
Measurement of reflectance made in such a way that specular reflectance is excluded from the measurement; diffuse reflectance only.
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Surround
Portion of the visual field immediately surrounding the central field or pattern of interest.
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Scattering
The process by which light passing through granular, fibrous or rough surface matter is redirected over a range of angles.
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Sequence
The order in which inks are deposited on paper by a printing press.
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Spectral Curve
A color?s ?fingerprint? ? a visual representation of a color?s spectral data. A spectral curse is plotted on a grid comprised of a vertical axis-the level of reflectance intensity; and a horizontal axis?the visible spectrum of wavelengths. The percentage of reflected light is plotted at each interval, resulting in points that form a curve.
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Spectral Data
The most precise description of the color of an object. An object?s color appearance results from light being changed by an object and reflected to a viewer. Spectral data is a description of how the reflected light has changed. The percentage of reflected light is measured at several intervals across its spectrum of wavelengths. This information can be visually represented as a spectral curve.
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Spectral Power Distribution (SPD)
Graphical or numerical representation of radiant energy per unit interval of wavelength for a given light source.
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Spectral
Pertaining to the visible spectrum, thus, having to do with color.
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Spectrophotometer
A photometric device for the measurement of spectral transmittance or spectral reflectance, an instrument that measures the characteristics of light reflected from or transmitted through an object, which is interpreted as spectral data.
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Spectrum
Spatial arrangement of electromagnetic energy in order of wavelength size. See Electromagnetic Spectrum, Visible Spectrum.
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Saturation
The attribute of color perception that expresses the degree of departure from a gray of the same lightness; grays have no saturation. Also referred to as chroma.
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Transmittance (of Light)
That fraction of the emitted light of a given wavelength which is not reflected or absorbed, but which passes through a material or object.
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Transmissive Object
An object that allows light to pass through from one side to the other. The color of a transmissive object results from the manipulation of wavelengths of light as they pass through.
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Turbidity
Reduction of transparency of a specimen due to the presence of particulate matter.
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Tristimulus
A method for communicating or generating a color using three stimuli either additive or subtractive colorants (such as RGB or CMY), or three attributes (such as lightness, chroma, and hue).
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Tristimulus Values
Amounts (in percent) of the three components necessary in a three-color additive mixture required for matching a color; in the CIE System, they are designated as X, Y and Z. The illuminant and standard observer color matching functions used must be designated; if they are not, the assumption is made that the values are for the 1931 observer (2 degree field) and Illuminant C.
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Transparent
Adjective to describe a material which transmits light without diffusion or scattering.
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Translucency
Appearance state between complete opacity and complete transparency; partially opaque.
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Total Color Difference (? or Delta E)
A single number that expresses the magnitude (size, degree, or amount) of a difference between two colors. The value tells nothing about the nature of the color difference.
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Tolerance
The amount of acceptable difference between a known correct standard (usually the customer?s specifications) and a set of measured samples. See Delta Error.
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Tint
A color produced by the mixture of white pigment or paint with a chromatic pigment or paint. The resulting mixture is lighter and less saturated.
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Thermochromism
A reversible change in color of a specimen due to change in temperature of the specimen. This is typical of highly saturated (vivid) colors (such as bright reds, yellows, and oranges).
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Transmission
Process by which incident light is transmitted through a material or object.
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Tristimulus Data
The three tristimulus values that combine to define or generate a specific color, such as R 255/G 253/B 0. Tristimulus data does not completely describe a color?the illuminant most also be defined. Also, in device-dependent color models such as RGB, the capabilities of the viewer or color-rendering device most also be defined. See Device Dependent.
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Ultraviolet
Radiant energy below 380 nm; portion of the electromagnetic spectrum between about 10 and 380 nm.
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Uniform Color Scale
A scale wherein the units of color difference that are judge to be equally different, are separated by nearly equal distances.
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Uniform Color Space
A color space in which equivalent numerical differences represent equivalent visual differences, regardless of location within the color space. A truly uniform color space has been the goal of color scientists for many years. Most color spaces, though not perfectly uniform, are referred to as uniform color spaces, since they are more nearly uniform when compared to the chromaticity diagram.
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Value (in Munsell)
An attribute of color used in the Munsell color system to indicate the lightness of a specimen viewed in daylight, on a scale from 0 for the ideal black to 10 for ideal white, in steps that are visually approximately equal in magnitude.
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Volume of Acceptability
The volume of acceptability is used to represent the location of acceptable trials in that color space. It is a three-dimensional region that surrounds a standard and is defined by tolerance values. If a trial falls within this volume, it is acceptable according to the tolerance criteria. If it falls outside this volume, it is unacceptable according to the tolerance criteria.
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Viewing Booth
An enclosed area with controlled lighting that is used in graphic arts studios, service bureaus, and printing companies as a stable environment for evaluating proofs and press sheets. Viewing booths are generally illuminated using graphic arts industry-standard D65 lighting, and are surfaced in neutral gray colors. See D65.
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Visible Spectrum
The region of the electromagnetic spectrum between 380 and 720 nanometers. Wavelengths inside this span create the sensation of color when they are viewed by the human eye. The shorter wavelengths create the sensation of violets, purples, and blues; the longer wavelengths create the sensation of oranges and reds.
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Wave
A physical activity that rises and then falls periodically as it travels through a medium.
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Wavelength
Light is made op of electromagnetic waves; wavelength is the crest (peak)-to-crest distance between two adjacent waves.
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White Light
Theoretically light that emits all wavelengths of the visible spectrum at uniform intensity. In reality, most light sources cannot achieve such perfection.
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White Reflectance Standard
A physical white standard of an imperfectly diffusing material, such as white ceramic, that is calibrated in reference to the perfect diffuser.
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Whiteness
Attribute by which an object color is judged to approach the preferred white.
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Wide Band Fluorescent
Generic term given to those fluorescent lamp products such as Cool White and Warm White that produce wide bands of visible light as a function of their phosphor blend.
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xyY (Chromaticity Coordinates)
A non-uniform color space in which colors are located within a three-dimensional rectangular coordinate system; x and y describe the chromaticity (hue and chroma) of a color. Y describes the luminosity (lightness or brightness) of a color.
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XYZ
The set of tristimulus values for numerically describing a color; calculated using ASTM E308-85.
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Yellow
One of the process ink colors for printing. Pure yellow is the ?blueless? color; it absorbs all wavelengths of blue from light and reflects all red and green wavelengths.
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