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Glossary
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A |
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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.
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. |
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B |
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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. 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 process inks. The letter "K" is
used to represent Black in the CMYK acronym to avoid confusion with
Bluefs "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. |
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C |
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Calibration: To check, adjust,
or systematically standardize the graduations of a device.
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 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 rednessgreenness 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 Internationale de lfEclairage):
A French name that translates to International Commission on Illumination,
the main international organization concerned with color and color measurement.
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/Greenness 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 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 y as the ordinate, which shows the spectrum locus (chromaticity
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 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 Chromaticity Coordinates: x
and y values that specify the location of a color within the CIE chromaticity
diagram.
CMC (Color Measurement 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.
CMYK: The subtractive primaries
cyan, magenta and yellow, plus black (k) which is required in the printing
process for more faithful reproduction. See Subtractive Primaries.
Color Management: Matching colors
between an original image, scanner, monitor, color printer and final
press sheet.
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 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 spectrumfs
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: 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.
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. |
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D |
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D50: The CIE 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.
D65: The CIE Standard Illuminant
that represents a color temperature of 6504°K.
Delta (?): A symbol used to indicate
deviation or difference.
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.
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 be 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.
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 Profile: Device-specific
color information that is a characterization of a devicefs 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 instrumentfs
range of measurable values, from the lowest amount it can detect to
the highest amount it can handle. |
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E |
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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 400 and 700 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. |
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F |
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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 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 create the illusion of different
colors. See CMY, Subtractive Primaries. |
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G |
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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.
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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H |
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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," "purple," Defined by its angular position in
a cylindrical color space, or on a Color Wheel. |
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I |
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ICC (International Color Consortium):
A group of hardware 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.
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 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
Illuminant for fluorescent illumination. F2 represents a cool white
fluorescent lamp (4200 K), F7 represents a broad-band daylight fluorescent
lamp (6500 K), and F11 represents a narrow-band white fluorescent lamp
(4000 K).
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. |
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K L |
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Kelvin (K): Unit of measurement
for color temperature.The Kelvin scale starts from absolute zero, which
is -273° Celsius.
L*a*b: A color space which represents
human visual perception and has equal spacing between colors. See CIELAB
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. 400 to 700nm).
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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M |
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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.
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. |
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N |
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Nanometer (nm): Unit of length
equal to 10-9 meter, or one millionth of a millimeter.Wavelengths are
measured in nanometers. |
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O |
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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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N P |
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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.
Photoelectric: Pertaining to the
electrical effects of light or other radiation-for example, emission
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 |
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R |
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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.
Reflectance: The percentage of
light that is reflected from an object. Spectrophotometers measure an
objectfs reflectance at various intervals along the visible spectrum
to determine the object colorfs spectral curve. See Spectral Curve,
Spectral Data.
RGB: The additive primaries red,
green, and blue. See Additive Primaries.
RIP: Raster Image Processor is
either a software program or hardware dedicated to the purpose of converting
certain file formats (typically vector graphics - such as page layout
files) into the rows of pixels (raster) that are the information in
the files which printers need to produce output. |
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S |
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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 colorfs "fingerprint"
- a visual representation of a colorfs 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 objectfs 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 or 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. 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: 100% cyan + 100% magenta = blue; 100% cyan
+ 100% yellow = green; 100% magenta + 100% yellow = red. |
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T |
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Tolerance: The amount of acceptable
difference between a known correct standard (usually the customerfs
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: 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).
Tristimulus Data: The three tristimulus
values that combine to define or generate a specific color, such as
R 255/G 255/B 0.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. |
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V W X Y |
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Viewing Booth: A 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.
Visible Spectrum: The region of
the electromagnetic spectrum between 400 and 700 nanometers.Wavelengths
inside this FONT 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 from light and reflects all red and green wavelengths.
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