Color Terms Glossary

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. 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, cyan, magenta, or yellow. 100% red + 100% green = yellow; 100% red + 100% blue = magenta; 100% green + 100% blue = cyan Adobe RGB An RGB working space that provides a relatively large gamut of colors and is well suited for documents that will be converted to CMYK. Appearance Manifestation of the nature of objects and materials through visual attributes such as size, shape, color, texture, glossiness, transparency, opaqueness, etc. Attribute Distinguishing characteristic of a sensation, perception or mode of appearance. Colors are often described by their attributes of hue, saturation, or chroma, and lightness. Black The absence of all reflected light; the color that is produced when an object absorbs all wavelengths from the light source.  When 100% cyan, magenta, and yellow colorants are combined, the resulting color, theoretically, is black. In real-world applications, this combination produces a muddy grey or brown. In four-color process printing, black is one of the process inks. The letter “K” is used to represent Black in the CMYK acronym to avoid confusion with Blue’s “B” in RGB. 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). See Lightness. Camera Raw A camera manufacturer’s proprietary format that captures all of the raw camera sensor data, along with metadata, that describes the camera settings. Color conversion The process of translating color values from one color space to another. Color gamut The total range of colors produced by a device. A color is said to be out of gamut when its position in one device’s color space cannot be directly translated into another devices color space. For example, the total range of colors that can be reproduced with ink on coated paper is greater than that for uncoated newsprint, so the total gamut for uncoated newsprint is said to be smaller than the gamut for coated stock. A typical CMYK gamut is generally smaller than a typical RGB gamut. Color settings file A color settings file (CSF) controls the key aspects of each applications color management behavior. Adobe Creative Suite 3 comes with several CSFs—each based on a common workflow—that offer preset color management policies and default profiles. Calibration To check, adjust, or systematically standardize the graduations of a device. The process of returning a device to known color conditions. Commonly done with devices that change color frequently, such as monitors (phosphors lose brightness over time) and printers (proofers and other digital printing devices can change output when colorant or paper stock is changed). Chroma The attribute of visual perception in accordance with which an area appears saturated with a particular color or hue. For example, a red apple is high in chroma; pastel colors are low in chroma; black, white, and grey have no chroma (this attribute of color is used in the color model L*C*H – Lightness, Chroma, Hue). This is also referred to as Saturation. Chromacity, Chromacity 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 Chromacity Diagram. CIE (Commission Internationale de l’Eclairage) A French name that translates to International Commission on Illumination, the main international organization concerned with color and color measurement. This committee developed a color model based on human vision. CIE94 The CIE94 tolerancing method utilizes three-dimensional ellipsoids as “containers” for color acceptance. CIE94 is conceptually similar to CMC2:1 but lacks some of the hue and lightness adjustments. It is expected that CIE94 will evolve over the next few years as additional studies are performed. 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/Greeness axis; and value b* represents the yellowness/blueness axis. CIELAB is a popular color space for use in measuring reflective and transmissive objects. CIE Standard Illuminants Known spectral data established by CIE for four different types of light sources. When using 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. See Illuminants. 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. CIE xy Chromacity Diagram A two-dimensional graph of the chromacity coordinates, x as the abscissa and y as the ordinate, which shows the spectrum locus (chromacity coordinates of monochromatic light, 380-770nm). It has many useful properties for comparing colors of both luminous and non-luminous materials. CIE Tristimulus Values Amounts of the three components necessary in a three-color additive mixture required for matching color: in the CIE Systems, 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 CIE 2° Standard Observer and Illuminant C. CIE Chromacity Coordiantes x and y values that specify the location of a color within the CIE chromacity diagram. CMC (Color Measurements Committee) Of the Society of Dyes and Colourists 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. CMY The subtractive primaries cyan, magenta, and yellow. See Subtractive Primaries. Color Management Matching colors between an original image, scanner, monitor, color printer, and final press sheet. Color Matching Function 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 Standard Observer. 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. Color Separation The conversion of red, green, and blue color information used in a computer into cyan, magenta, yellow, and black channels that are used to make printing plates. 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. Characterization The process of creating a profile that describes the unique color conditions found on a particular device. For monitors, this includes colorimetric descriptions of its phosphors and the color temperature of its white point. For printers, this includes descriptions of the inks, paper stock, and line ruling. In a CMS, you characterize the calibrated monitor by creating an ICC device profile. Color Management Color management is the process by which you try to match color conditions in a set of devices (e.g., scanner, monitor and printer). These devices produce color using different methods; therefore, they may display the same color value differently, and may not all display the same range of color values (see color gamut, below). In other words, color is device-dependent: the color that you see will change depending on the device that's producing it. A color management system (CMS) is a collection of color management software tools used to try to make color device-independent. Ideally, the colors on your monitor should accurately represent the colors in a scanned image, and the colors you see on the final output. A CMS maps colors from the color gamut of one device into a device-independent color space, and then maps those colors to the color gamut of another device. CMM Color Matching Method, also called a Color Engine. The specific software component in a CMS that does the color conversion calculations from one device's color space to another using the ICC device profiles (e.g., ColorSync or Kodak CMS). Color Engine See CMM. Color Model The dimensional coordinate system used to numerically describe colors. Some models include : Red, Green, Blue (RGB); Hue, Lightness, Saturation (HLS); Cyan, Magenta, Yellow, Black (CMYK); and Lightness, a, b (Lab). Color Space A three-dimensional geometric representation of the colors that can be seen and/or generated using a certain color model. The specific range of colors in a particular model (e.g. , RGB, Lab, CMYK). For example, if you have an RGB master image and convert it to CMYK using an ICC device profile for a CMYK composite printer, then, using the same master RGB document, convert the image to CMYK using a different ICC device profile, each resulting CMYK image will be in a different CMYK color space. Also called Gamut. Colorimeter A device that measures the luminosity of RGB light. When used with software, it can be used to create ICC device profiles for monitors. This optical measurement instrument responds to color in a manner similar to the human eye – by filtering reflected light into its dominant regions of red, green, and blue. Colorimetric Of or relating to values giving the amounts of three colored lights or receptors – red, green, and blue. ColorSync Built-in color management architecture for Apple Macintosh computers. Third-party vendors utilize the ColorSync framework to provide device calibration, device characterization, and device profile-building methods. 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 temperatures such as 2400°K are red; higher temperatures such as 9300°K are blue. Neutral temperature is grey, at 6504°K. Color Wheel The visible spectrum’s continuum of colors arranged into a circle, where complementary colors such as red and green are directly across from each other. Colorants Materials used to create color-dyes, pigments, toners, phosphors. Contrast The level of variation between light and dark areas in an image. Control Limits The amount of acceptable variation in press capabilities over the course of a press run. Cyan One of the process ink colors for printing. Pure cyan is the “redless” color; it absorbs all red wavelengths of light and reflects blue and green wavelengths. D50 The CIE Standard Illuminant that represents a color temperature of 5000°K (daylight). This is the color temperature that is most widely used in graphic arts industry viewing booths. See Illuminants D. D65 The CIE Standard Illuminant that represents a color temperature of 6504°K (Daylight). See Illuminants D. Delta (∆) A symbol used to indicate deviation or difference. Delta (∆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 chromacity differences, ∆a* and ∆b*, and the Lightness difference, ∆L. See CIE 94. Destination (output) profile An ICC color profile representing the device or color space for which color values are converted in order to preserve color appearance. see Output Profile. Device-Dependent Describes a color space that can be defined only by using information on the color-rendering capabilities of a specific device. For example, the RBG 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 scanners, printers, and printing presses. 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. Dye A soluble colorant as opposed to pigment, which is insoluble Dynamic Range An instruments range of measurable values, from the lowest amount it can detect to the highest amount it can handle. Electromagnetic Spectrum The massive band 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. 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. 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. Gamut The range of different colors that can be interpreted by a color model or generated by a specific device. 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. Hue The basic color of an object, such as “red,” “green,” “purple,” etc. Defined by its angular position in a cylindrical color space, or on a Color Wheel. ICC The International Color Consortium established in 1993 by eight industry vendors (including Adobe Systems) to create, promote, and encourage the standardization and evolution of an open, vendor-neutral, cross-platform color management system architecture and components. For more information, see www.color.org. ICC Device Profile A file that describes how a particular device (e.g., monitor, scanner, printer, or proofer) reproduces color (i.e., its specific color space). by mapping color values to a device-independent color space like CIE XYZ or CIELAB. Profiles can be either generic or custom.

1. Generic device profiles are created by the device manufacturer, who examines the color characteristics of a group of the same devices under controlled conditions, using device profiling software and instruments.
2. Custom device profiles are created for a individual device, using a color measuring instrument (e.g., a spectrophotometer or colorimeter) and device profiling software.

Illuminant Incident luminous energy specified by its spectral distribution. Illuminant A (CIE) CIE Standard Illuminant for incandescent illumination, yellow-orange in color, with a correlated color temperature of 2856° K. Illuminant C (CIE) CIE Standard Illuminant for tungsten illumination that simulates average daylight, blueish in color, with a correlated color temperature of 6774° K. Illuminants D (CIE) CIE Standard Illuminant 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. Illuminants F (CIE) CIE Standard Illuminants for fluorescent illumination. F2 represents a cool white fluorescent lamp (4200K), F7 represents a broad-band daylight fluorescent lamp (6500K), and F11 represents a narrow-band white fluorescent lamp (4000K). Intensity Saturation or reflective energy as related to visible wavelengths of light. Reflectance of wavelengths at high intensity generates high saturation, or chroma. 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 Kelvin(K) Unit of measurement for color temperature. The Kelvin scale starts from absolute zero, which is -273° Celsius. 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. Light Electromagnetic radiation in the spectral range detectable by the human eye (approx. 380 to 720 nm). Lightness The attribute of visual perception in accordance with an area appears to emit or reflect more or less light. Also refers to the perception by which white objects are distinguished from grey objects, and light from dark colored objects. 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. 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. Monitor RGB Same as RGB; monitor RGB simply refers to the color space that can be achieved by a particular monitor using combinations of red, green, and blue light. 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. Nanometer (nm) Unit of length equal to 10° meter, or one millionth of a millimeter. Wavelengths are measured in nanometers. 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 theses patches allows press operators to determine trap value. The term Overprint also applies to any object printed on top of other colors. 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. Photoelectric Pertaining to the electrical effects of light or other radiation -- for example, the emission of electrons. Photoreceptor the cone and rod shaped neurons that cover the retina of the eye. Photoreceptors are excited by visible wavelengths, and then send signals to the brain where the sensation of color is perceived. Pigment An insoluble colorant; as opposed to dye, which is soluble. Pixel A tiny picture element that contains red, green, and blue information for color rendering on a monitor or 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). Primary Colors The dominant regions of the visible spectrum: red, green, and blue; and their opposite colors cyan, magenta, and yellow. See Additive Primaries, Subtractive Primaries. 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. 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. Process Printing Output based from a printing press that uses four colors (cyan, magenta, yellow, and black) to create the illusion of continuous tone images. By depositing combinations of the subtractive primaries cyan, magenta, yellow, and black ink on paper to achieve an image. These colorants are deposited as dots of different sizes, shapes, and angles to create the illusion of different colors. See CMY, Subtractive Primaries. Proofer A printing device a service bureau uses to create images as contracts (also called a contract proof) to match in the final output from the offset press. Traditional proofers create prints from negative separations; digital proofers create ink-jet (e.g., IRIS) or dye-sublimation (e.g., Kodak, 3M) composite prints. Profile Connection Space (PCS) A reference color space is a device-independent theoretical color model used by a CMM (color engine) for translating colors from one device's gamut to another. The CIE Lab is an example of a Reference Color Space. This component is built into the CMM, it is neither alterable nor visible to users. This is sometimes as the Reference Color Space. Reflective Object A solid object that returns some or all of the wavelengths of light that strikes its surface. A reflective object that returns 100% of all light is called a perfect diffuser – a perfectly white surface. 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. RGB The additive primaries red, green, and blue. See Additive Primaries. Rendering Intents The method a CMM uses for converting (i.e., mapping) colors from one device's gamut to another. The three methods are called Perceptual, Saturation, and Relative Colorimetric. In InDesign and Illustrator the names of the rendering intents are called Image, Graphics, and Colorimetric, but they do the same thing. Perceptual/Image: Compresses the total gamut from one device's color space into the gamut of another device's color space when one or more colors in the original image is out of the gamut of the destination color space. This preserves the spectral relationship between colors and prevents "clipping," which is where distinctly different colors in one color space appear the same in the destination color space. The disadvantage of this render intent is that all of the original colors will change. Saturation/Graphics: Reproduces the original image color saturation (vividness) when converting into the target device's color space. Primarily designed for business graphics, where exact relationships between colors (such as in a photographic image) are not as important as bright colors. Relative Colorimetric/Colorimetric: When a color in the current color space is out of gamut in the target color space, it is mapped to the closest possible in gamut color in the target color space, while colors that are in gamut are not affected. This render intent can cause two colors which appear different in the current color space to be the same in the target color space. This is called "clipping." This is the method of color space translation built into Photoshop 4.0 and earlier. Saturation the attribute of color perception that expresses the amount of departure from the neutral grey of the same lightness. Also referred to as Chroma. Sequence The order in which inks are deposited on paper by a printing press. Spectral Curve A color’s “fingerprint” – a visual representation of a color’s spectral data. A spectral curve 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. 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 was 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. Spectrum Spatial arrangement of electromagnetic energy inn order of wavelength size. See Electromagnetic Spectrum, Visible Spectrum. Standard An established, approved reference against which instrument measurements of samples are evaluated. Subtractive Primaries Cyan, Magenta, and Yellow. Theoretically, when all three subtractive primaries are combined at 100% on white paper, black is produced. When those 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: 100% cyan + 100% magenta = blue; 100% cyan + 100% yellow = green; 100% magenta + 100% yellow = red. Spectrophotometer An instrument that measures the characteristics of light reflected from or transmitted through an object, which is interpreted as spectral data. sRGB A standard working space developed by Microsoft and Hewlett-Packard describing the color of the “average” or “standard” home computer monitor. 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. 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. Tristimulus 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). Tristimulus Data The three tristimulus values that combine to define or generate a specific color, such as R225/G225/B0. Tristimulus data does not completely describe a color – the illuminant must also be defined. Also, in device dependent color models such as RGB, the capabilities of the viewer or color-rendering device must also be defined. See Device-Dependent. 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 grey colors. See D65. 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. Wave A physical activity that rises and then falls periodically as it travels through a medium. Wavelength Light is made up of electromagnetic waves; wavelength is the crest (peak)-to-crest distance between two adjacent waves. White Light Theoretically, light that emits all wavelengths of the visible spectrum at uniform intensity. In reality, most light sources cannot achieve such perfection. Yellow One of the process ink colors for printing. Pure yellow is the “blueless” color; it absorbs all wavelengths of blue light and reflects red and green wavelengths. U.S. Web Coated (SWOP) v2 A CMYK working space profile based on the U.S. standard for publication printing presses, governed by the Specifications for Web Offset Publications (SWOP). This standard was developed in 1972 for publications such as magazines and catalogs printed on offset presses.