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, either cyan, magenta, or yellow.
100% red + 100% green = yellow; 100% red + 100% blue = magenta; 100% green + 100% blue = cyan
See subtractive primaries.
Appearance: Manifestation of the nature of objects and materials through visual attributes such as size, shape, color, texture, glossiness, transparency, opacity, 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 gray or brown. In four color process printing, black is one of the 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.
Chroma: The attribute of visual perception in accordance with which an area appears saturated with a particular color or hue. Example: a red apple is high in chroma; pastel colors are 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.
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.
CIE (Commission International de L'Eclairage): A French name that translates to International Commission on Illumination, the main international organization concerned with color and color measurement.
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.Arch. 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 the 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.
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 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 monachromatic light, 380-770nm). It has many useful properties for comparing colors of both luminous and nonluminous materials.
CIE Tristimulus Values: Amounts (in percentages)O 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 CIE 2° Standard Observer and Illuminant C.
CIE xyz Chromaticity Coordinates: Plotted to for the xyY chromaticity diagram which visually represents the gamut of vision for the 1931 CIE 2° Standard Observer. Calculated from the CIE XYZ Tristimulus Values.
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 rectangular coordinates of the CIELAB color space.)
CMY: The subtractive primaries cyan, magenta, and yellow. See Subtractive Primaries.
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.
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 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.
Color Space: A three-dimensional geometric representation of the colors that can be seen and/or generated using a certain color model.
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.
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 gray, 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 located directly across from each other.
Colorants: Materials used to create colors, dyes, pigments, toners, phosphors.
ColorSync: Building 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.
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.
Colorimetric: Of or relating to values giving the amounts of three colored lights or receptors, red, green and blue.
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 all blue and green wavelengths.
D65: The CIE Standard Illumination that represents a color temperature of 6504°K. This is the color temperature that is most widely used in graphic arts industry viewing booths. See Kelvin (K).
Delta: A symbol used to indicate deviation or difference.
Delta Error(E): In color tolerencing, 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.
Densitometer: A sensitive, photoelectric instrument that measures the density of images or colors.
Density: The ability of a material to absorb light; the darker it is, the higher the density.
Device Dependent: Describes a color space that can re 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 additional, all monitors have different capabilities and limitations, as do different 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.
Device Profiler: 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.
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 lass 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.
Four Color Process: Depositing combinations of the subtractive primaries cyan, magenta, yellow, and black on paper to achieve. These colorants are deposited as dots of different sizes, shapes, and angles to create the illusion of different colors. See CMY, Subtractive Primaries.
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 processing printing. See Gamut.
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.
HiFi Printing: Process printing that expands the conventional four color process gamut using additional, special ink colors.
Hue: The basic color of an object, such as "red," "green," etc. Defined by its angular position in a cylindrical color space, or on a Color Wheel.
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, bluish in color, with a correlated color temperature of 6774°K.
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.
Intensity: Saturation or reflective energy as related to visible wavelengths of flight. Reflect range of wavelengths at high intensity generates high saturation or chroma.
IT8: Series of test targets and tools for colorcharacterization 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 720nm).
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.
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 specifically 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 a 10-9 meter, or one millionth of a millimeter. Wavelengths are measured in nanometers.
Overprint: On a press sheet color bar, overprints are color patches were two process inks have been printed, one atop the other. Checking the density of these patches allows press operators 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, emissions of electrons.
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 where the sensation of color is perceived.
Pigment: An insoluble colorant; as opposed to a dye which is soluble.
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).
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.
Reflective Object: A solid object that returns some or all of the wavelengths of emitted light that strike 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.
Saturation: The attribute of color perception that expresses the amount of departure from the neutral gray 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); 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.
Spectrophotometer: An instrument that measures the characteristics of light reflected from our transmitted through an object, which is interpreted as spectral data.
Spectrum: Spatial arrangement of electromagnetic energy in 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. 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.
100% cyan + 100% magenta = blue; 100% cyan + 100% yellow = green; 100% magenta + 100% yellow = red.
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.
Tranmissive 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.
Tri-stimulus: 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.)
Tri-stimulus Data: The three tri-stimulus values that combine to define or generate a specific color, such as R255/G255, B 0. Tri-stimulus 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 65 lighting, and are surfaced in neutral gray colors.
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 or 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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