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.
Achromatic : The attribute of light from a surface or light source that relates to the amount of light. It is brightness.
Additive primaries : Three light sources chosen so that they can reproduce other colors by addition of wavelengths. One primary contributes long wavelengths (Red), another the medium wavelengths (Green), and the other the short wavelengths (Blue).
Anisotropy : The phenomenon whereby a printer produces slightly different color depending on the orientation of the paper movement through the printer.
Aperture : A small opening that light comes through. Color-matching experiments usually involve the test subject viewing colors through a small aperture, and measurement instruments also view samples through a small aperture.
Artifact : Something added artificially. In general, any undesirable effect that is visible in a displayed or printed image, but was artificially introduced by the equipment or software. E.g banding compression artifacts, moire patterns, etc.
Attribute : Distinguishing characteristic of a sensation, perception or mode of appearance. Colors are often describedtheir attributes of hue, saturation or chroma, and lightness.
Banding : An artifact where there are noticeable jumps from one tone level to the next.
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, but in real world applications this combination produces a muddy brown. That is why in printing we use black ink. The letter “K” is used to represent black in the CMYK acronym to avoid confusion with Blue’s “B” in RGB.
Black generation : In four-color printing, the method used to generate the black, or K, channel from the color channels. The two main kinds of black generation are UCR and GCR.
Black point : The density, and occasionally the color, of the darkest black reproducible by a device. For a printer, this is the density and neutral color balance of the darkest black achievable using the printing inks. For a monitor this is the density of the monitor when displaying black, and can be adjusted by setting the black level.
Black level : On a monitor, the setting that controls the base black of the display. On a CRT, this is just the brightness (offset) control on the monitor.
Black point compensation : A setting in Adobe Photoshop that makes sure that the black point in the source profile is mapped to the black point of the destination profile, and the rest of the tonal range is scaled accordingly.
Blackbody radiator : A light source whose photons are entirely due to heat energy given off by the source. According to the laws of physics, there is a very predictable correlation between the temperature of the blackbody and the color of the light. Lower temperatures are red, higher temperatures are white, and the highest temperatures are blue.
Brightness : The perceived response to light intensity. This response in non-linear (in a human observer).
Calibration : Modifying or adjusting the behavior of a device (such as a color reproduction device or a measurement instrument) to a desired state (often a factory specification, or some state that helps simulate some other device).
Camera metamerism : The type of metamerism where two color samples match to a human observer, but not to a certain camera, or vice versa (the human does not see a match, but the camera does).
Candela : The unit of luminous intensity.
CCD : Charged-Coupled Device. A light sensitive microchip, used in scanners and digital cameras as the basis for capturing a digital image.
Chroma : Technical word for saturation. The attribute of visual perception in accordance with which an area appears saturated with a particular color or hue. Black, white and gray have no chroma.
Chromatic : The attributes of light from a surface or light source related to the wavelength composition of the light. Specifically its hue and saturation. Contrast with achromatic. The chromatic attributes describe the properties of the photons in the light, while the achromatic component describes the quantity of photons in the light.
CIE : Commission Internationale d’Eclairage (International Commission on Illumination). An international association of color scientists that has assembled many of the standards used as basis for colorimetry.
CIE LAB : (Also known as L*a*b*). One of the two main color spaces proposed by the CIE to attempt perceptually uniform color space. L* is the lightness value, a* is the red-green opponency,and b* is the blue-yellow opponency. CIELAB is one of the two color spaces used as a PCS in ICC-based color management.
CIE LCh : (Also known as LCH, for Lightness, Chroma, Hue). A derivative of CIELAB that uses polar coordinates rather than rectangular ones, often employed as a user interface for manipulating device independent data. The LCh space is cylindrical: lightness runs along the vertical axis from white (100) to black (0), Chroma (saturation) is represented by the distance from the central axis, and hue is represented by the angle around the cylinder, with reds around 0 degrees, yellows around 90 degrees, greens around 180 degrees and blues around 270 degrees.
CIE Luv : (Also known as L*u*v*). One of the two color spaces proposed by the CIE to attempt a perceptually uniform color space.
CIExy diagram : (Also known as the CIExy chromaticity chart). The horseshoe-shaped diagram representing the relationships of the colors in the CIE system.
CIE XYZ: Shorthand for the CIE XYZ color space. This defines colors in terms of three theoretical primaries X,Y,Z, that are based on the CIE research into human color response (the CIE Standard Observer). XYZ is not perceptually uniform and therefore can not be used for computing color distance. XYZ is one of the two color spaces used as a possible PCS in ICC-based color management.
Click-balancing : Gray-balancing an image by clicking on an area in the image that you known should be neutral.
CMM : Color Management Module : some people know it as an abbreviation of Color Matching Method, or Color Manipulation Model. In any case the CMM is a drop in component that provides the engine for profile to profile conversions. It defines how colors are computed using the sample points in the profiles as guidelines.
CMS : Color Management System. Software dedicated to handling device to device conversion of colors. The ICC-based model for a CMS consists of four components: a PCS, device profiles, a CMM, and a set of rendering intents.
Colorant : Something, such as a dye or pigment, or phosphors on a monitor, that produces color on some other medium.
Color bar : A strip of color patches, usually printed in the margin of a printed page, and used for process control. A color bar is by definition device-dependent and should be created in the color model of the printing device. Color bars contain at least the maximum (100%) of each primary and complementary color. Many also contain 50% coverage areas of primaries and their overprints, as well as neutrals.
Color constancy : The tendency of the visual system to consider the color of an object to be constant despite changing viewing conditions. If all the colors in a scene change in the same way, the eye tends to attribute this to a change in illuminant, and discounts the change.
Color-mixing function : In a visual system or color-measurement device (such as a camera, or colorimeter), the unique mixture of red, green, blue responses to different color samples. Visual systems and measurement devices don’t actually have a gamut, they have a color-mixing function.
Color model : A general system for assigning numbers to colors. An example would be the RGB color model, where each color is defined in terms of three numbers, the first the amount of some (as yet undefined) red primary, the second a green primary, and the third a blue primary. Contrast with color space.
Color space : An instance of a color model in which every color is represented by a specific point in space, and thus has a specific set of three or more numbers that describe it. An example would be the RGB space of a particular monitor, where a certain color has a specific set of three numbers representing the amounts of the red, green and blue needed to produce that color. Note that there can be many color spaces that use the same color model.
Color temperature : A description of the color of the light in terms of the temperature of the light source, in kelvins. Lower temperatures are redder, higher temperatures are white, and the highest temperatures are bluer. Technically we should only refer to the exact color temperature of a blackbody radiator. If the light source is not a true blackbody radiator, then it is more correct to speak of the correlated color temperature of the light source.
Colorant : Something used to produce color, such as the dyes in inks or toner, or the phosphors in a monitor.
Colorimeter : A device for computing colorimetry (color matches) from measurements of a surface.
Colorimetric intent : The two rendering intents that try to preserve colorimetry of colors. Colors are mapped to an exact match wherever possible, and where not possible (because the color is out of the target gamut), the color is mapped to it’s nearest equivalent. In most cases, this conversion should include a remapping of the white point so that this colorimetric match is relative to the target white point. This is known as relative colorimetric. In some cases (In certain stages of proofing), the colorimetric match should be absolute. The colors should be converted as if the match were being done relative to the source device’s white point. This is known as absolute colorimetric.
Colorimetry : The science of predicting color matches based on ever-growing research into typical human color vision. Much colorimetry is based on the work of CIE.
ColorSync : Apple’s implementation of ICC-based color management. On Macintosh computers, the components in the Mac OS that handle such things as making profiles and CMMs available to programs that need to convert colors.
Complementary colors : Two colors that make gray (or white) when combined. For example blue and yellow are complementary colors.
Continuous tone : A device that can represent many tonal values for each unit pixel. A laser printer is not continuous tone as it can only lay down a printer dot or leave it blank. To produce tones, it needs to use the trick of screening. A monitor is continuous tone as every displayed pixel can represent tone levels by varying the intensities of the red, green and blue light.
Contone : Shorthand for continuous tone.
Contrast : The difference between the lightest and darkest areas of an image.
CRD : Color Rendering Dictionary. In PostScript color management, the CRD is the equivalent of the destination profile, and either resides in the RIP or is sent to it at print time.
CRI : Color Rendering Index. A measure of how well colors are rendered by different lighting conditions as compared to a standard light source. CRI values range from 1 to 100, whereby 100 means that all colors that match under the standard would also match under the measured lighting conditions.
CRT : Cathode Ray Tube. The most common type of computer monitor until 2000, consisting a flattened end coated with phosphors that glow when excited by the electrons.
CSA : Color Space Array. In PostScript color management, the CSA is the equivalent of an ICC source profile that is downloaded to a PostScript RIP together with the documents it describes.
Curing time : Time needed after printing by some colorants. For example, the inks in inkjet printers, for the printed image to arrive at a stable appearance.
D50 : One of the CIE standard illuminants. D50 is a specification of daylight with a correlated color temperature of 5000 K.
D65 : One of the CIE standard illuminants. D65 is a specification of daylight with a correlated color temperature of 6500 K. this is the standard white point that we recommend for monitor calibration.
ΔE (delta E) : Generically, the computed degree to which two colors appear to match. Usually calculated in CIELAB, but it can be calculated to other color differencing systems.
Densitometer : A device for computing density from measurements of a surface.
Density : The degree to which a surface absorbs light. Density is a logarithmic value.
Destination profile : In color conversion, the profile that defines how to convert colors from the profile connection space (PCS) to the target color space.
Device-dependent : The property of a color model whereby the exact meaning of a set of numbers depends on the specific device. For example RGB is a device-dependent color model because a specific set of RGB numbers (say, 112, 40, 230) will mean a different thing. In example it will produce a different color, depending on what RGB device you are using.
Device-independent : The property of a color model where the exact meaning of a set of numbers is unambiguous and does not depend on any specific device. For example LAB is device-independent because a specific set of LAB numbers means the same thing – it represents the same color, regardless of any device.
Display profile : Also known as monitor profile. A profile for a display device such as a computer monitor.
Dithering : (1) Screening. (2) Any technique that simulates colors or tones by intentionally printing or displaying dots of various primary colors in various patterns to give the illusion of a larger set of colors. A halftone is a type of dither (called an ordered dither) where the dot pattern is uniform and uses the primary ink colors together with paper white to give the illusion of many colors. Another example of dithering can be seen when viewing a full-color image on a monitor in 256-color mode. The illusion of additional colors is created by displaying the limited palette of 256 primary colors in various dot patterns.
Dot gain : The growth of halftone dots during print reproduction. The main cause of dot gain is the spreading of ink as it hits paper, but slight dot gain can also be introduced during imaging to film.
Dpi : Dots Per Inch. Usually, but not always, used when referring to the resolution of printers. Often incorrectly used as synonymous with ppi, or sometimes spi.
Dye : A soluble colorant. Dye-based inks exhibit color drift over time, especially when exposed to light and other elements. Often used in inkjet printers. Contrast with pigment.
Dynamic range : A range from brightest white to darkest dark as measured in density. The dynamic range of measurement devices (such as scanners, cameras, or densitometers) describes the distance between the darkest black the device can measure before it is unable to detect differences in brightness, and the brightest white it can measure without overloading. Also applied to media (for example, prints or transparencies) and images, to describe the range from the darkest black to the brightest white.
Early-binding : A workflow strategy that converts all colors to the final output space as soon as possible. For example converting all scans immediately to printer CMYK.
Editing space : A color space intended specifically for editing of color values. An RGB editing space should ideally: be gray-balanced, be perceptually uniform, and have a gamut large enough to contain the values being edited.
Electrophotostatic : The class of printing devices that use a laser to set a static charge on a point-by-point basis, to control where toner particles stick.
Embedding a profile : Saving a profile in a document file. The profile defines the source profile used when converting the color values in the file to any other color space. The embedded profile effectively provides the meanings of the color numbers in the file.
Emissive : Having the property of emitting light. A lightbulb and a computer monitor are emissive.
Encoding : (1) In a color space, a specific set of numerical values that can represent a specific color. For example, in a monitor’s RGB space, each encoding is a specific triplet of 8-bit numerical values, and approximately 16.7 million encodings are available. (2) The act of assigning specific numerical values to colors.
Error diffusion : A form of FM screening.
Fluorescence : The absorption of light energy at one wavelength and re-emission at a different wavelength.
FM screening : In printing, a method of screening in which the dots are all the same size, but the effect of tones is created by varying the frequency of the dots in a given area (hence “frequently modulation”). Contrast with AM screening.
Fovea : The area at the center of the retina that is populated predominantly by cones. This is where color vision occurs and where visual acuity (sharpness) is highest.
Foveal vision : The viewing condition where the image is focused on the fovea of the viewer, and thus produces the best acuity and color vision.
Gamma : (1) The degree to which a device or color space is non-linear in tonal behavior, represented as the exponent of a power function. (2) In CRT display systems, the relationship between input voltage and output luminance. (3) In color spaces, the mapping of tonal values to perceived brightness. A gamma value of around 2.2 is generally considered perceptually uniform.
Gamma curve : A simple example of a tone reproduction curve typical of most devices. This is a simple non-linear curve.
Gamut : The range of colors and density values reproducible on some output device such as a printer or monitor. This is sometimes split into the color gamut. The range of colors limited by the primaries used and the dynamic range – the range of brightness levels from the darkest black to the brightest white of the device.
Gamut compression : The remapping of color and tone values from a large gamut to a smaller one.
Gamut mapping : The remapping of color and tone values from one color space to another. If the destination color space has a smaller gamut, this remapping will require gamut compression.
GCR : Gray Component Replacement. A method of black generation that replaces an amount of CMY with the equivalent amount of K.
GDI : Graphics Device Interface. Microsoft’s name for the display engine in Windows.
Gray-balanced : A color space in which any neutral pixel has equal R,G and B values is said to be gray-balanced.
Gray-balancing : (1) Correcting RGB values in an image so that neutral grays have balanced R,G and B values. (2) Adjusting the behavior of a device to achieve good reproduction of neutrals.
Halftone : In printing, the most commonly used method for screening. The effect of tones is created by dividing the image into equally spaced halftone cells, each of which is filled with a dot of known size. Larger dots create darker tones and smaller dots create lighter tones.
High-bit : A general term for anything higher than the minimum 8 bits per channel (256 tone levels). A high-bit file is a 16 bit file.
HLS : An adaptation of the RGB color model, stands for hue, lightness, saturation. When lightness is at maximum, the color is white.
HSB : An adaptation of the RGBcolor model, stands for hue, saturation, brightness. Common in many color-managed applications. Similar to HLS except that when brightness is at maximum, the color is at its brightest.
HSV : An adaptation of the RGB color model, stands for hue, saturation, value, and is synonymous with HSB.
Hue : The property of the light from a surface or light source by which we perceive its dominant wavelength.
ICC : International Color Consortium. A consortium of color-related companies that have cooperated to standardize profile formats and procedures so that programs and operating systems can work together.
ICM : Image Color Management. The implementation of the ICC profile specification in Microsoft Windows.
Illuminant : A light source defined spectrally. In other words, by the relative amount of energy at each point in the visible spectrum.
Infrared : (IR) The non-visible region of the electromagnetic spectrum just below the low-energy, or red end, of the visible spectrum.
Input profile : A profile for an input device such as a camera or digital camera.
Intensity : The sheer amount of light from a surface or light source, without regard to how the observer perceives it; the number of photons in the light. Compare to brightness, which is the perception of the light intensity.
Interpolation : The computation of unknown values that fall between known values (usually measures or sampled).
ISO : The International Organization For Standardization. An organization that coordinates networks of standards bodies around the world.
IT8 : One of a family of targets used for calibration and profiling of scanners and printers.
Kelvins : (K) The unit physicists use to describe temperature, with the scale starting at absolute zero, the temperature at which all atomic activity stops.
Late-binding : A workflow strategy that delays conversions to final output as long as possible, perhaps even doing the conversion in the RIP.
LCD : Liquid Crystal Display. A common type of computer monitor, consisting of two layers of polarized plexiglass between which are liquid crystals that change shape in response to electrical currents.
Lightness : Relative brightness. The brightness of a surface or a light source relative to some absolute white reference.
Linear : A simple relationship between stimulus and response, whereby doubling the stimulus produces double the response. The human sensory system is predominantly non-linear.
Linearization : (1) Calibration. (2) The act of making a device linear (which is a specific form of calibration).
Logarithmic : A method of arranging numbers on a scale that compresses as the numbers get larger. This is convenient when the same scale has to represent both very small and very large numbers.
Lookup table : (LUT) A table that allows input values to be looks up and replaced by corresponding output values. For example, an RGB to XYZ lookup table would let you (or a color management system) look up an RGB triplet and find the equivalent XYZ triplet.
Lpi : Lines Per Inch. This always refers to the resolution, or screen frequency, of a halftone. Not to be confused with Dpi, which refers to the resolution of the microdots used by a digital printer, not the resolution of halftone dots.
Luminance : The amount of light energy given off by a light source, independent of the response characteristics of the viewer. More precisely, luminance is the luminous intensity per unit area of the light-emitting surface.
Luminous intensity : The amount of light energy given off over time from a point light source. This is measured in candelas.
Matrix : An ordered set of numbers listed as a rectangular grid. A 3X3 matrix can be used to convert from one 3-channel space to another. For example, it can convert any triplet of numbers representing the RGN values of a color, to another triplet of numbers representing the CIE XYZ values for the color. All profiles use either a 3×3 matrix, or a lookup table (LUT), to convert values.
Measurement geometry : The physical geometry of a measurement device that defines the relative angles of the light source, measured surface, and detector. These are important when dealing with such effects as glare and surface texture on the measurements.
Memory color : A color – such as a skin tone, grass, or sky blue – that has a special association for the viewer, and is therefore more important to get right than other colors for which the viewer has no memory reference.
Metameric ink / dye : A slight, but common misuse of the term metamerism. When someone says that the printer has metameric inks, he generally mean that the inks are vulnerable to wide shifts in apparent color depending on lighting conditions.
Metamerism : The condition where two color samples, with different spectral properties, produce the same color sensation under certain viewing conditions, and a different color sensation under different conditions.
Metamers : Two color samples that exhibit metamerism. In other words, they match under some, but not all, viewing conditions.
Monitor profile : Also known as a display profile. A profile for a computer monitor.
Monitor RGB : The color space represented by the display profile.
Monochromatic light : Light consisting of photons all the same energy level or wavelength. An example would be a laser.
Non-linear : A complex relationship between stimulus and response, where (for example) increasing the stimulus produces less and less response. The human sensory system is predominantly non-linear.
Null transform : When the source profile and destination profile are the same, CMMs ensure no conversion occurs.
Observer metamerism : The type of metamerism where two colors samples match to one observer, but not to another observer. Examples of this are scanner metamerism and camera metamerism.
Opponency : The theory of color vision (now well verified by experiments) that we experience color in terms of various opponent pairs: red-green, blue-red, and light-dark. This has now been reconciled with trichromacy with research that shows that one layer of the retina has the three photoreceptors, and the next layer seems to sort this information into the opponent pairs.
Ordered dither : by this we mean a halftone.
Output profile : A profile for an output device such as a printer or proofing device. Not to be confused with a destination profile.
PCS : Profile Connection Space. The color space used as the intermediate form for conversions from one profile to another. In the ICC specification, the PCS is either CIE XYZ or LAB.
Perceptual intent : The rendering intent that tries to preserve the perceptual relationships in an image, even if this means remapping all colors both in-gamut and out of gamut. This is usually, but not always, the preferred rendering intent for images that contain many out of gamut colors, but if all colors are in-gamut for the target color space, relative colorimetric may be preferred.
Perceptually uniform : The property of a color space whereby distances between points in the space correspond well to perceived distances between the colors they represent. Close colors are represented by close points. Different colors are represented by distant points.
Phosphor : A substance that absorbs energy and gives off photons, usually of a very specific wavelength. The photons are not the result of heat energy (in other words, this is not blackbody radiation), but rather of specific properties of the atoms in the substance.
Photon : A fundamental packet of electromagnetic energy travelling through space. In some ways photons behave like particles and in other ways photons behave like waves.
Photoreceptors : Light – sensitive nerve cells in the retina. (sometimes called simply receptors). The two main types of photoreceptors are rods and cones, so called because of their shape. Rods are responsible for low-light vision, and cones for daytime vision. There are three types of cones, each sensitive to a different part of the visible spectrum.
Pigment : An insoluble colorant. Pigment-based inks greater stability over time, even exposed to light (including UV) and other elements, than dye-based inks. Used in press inks, toners, and outdoor printing. Contrast with dye.
Polarization : Filtering light in such a way that only light waves of a particular orientation pass. Polarization is a key part of how LCD monitors work. Many measurement instruments also incorporate polarizing filters to reduce glare issues with glossy targets.
PPi : Pixels Per Inch : this is usually used when referring to the resolution of a digital image. Contrast with dpi.
Primaries : Shorthand for color primaries. A set of colors that, used together in controlled amounts, can reproduce all other colors.
Process color : The combination of three or more primeries, in various amounts, to simulate the reproduction of full color. In printing, often used as a shorthand for four-color process printing using cyan, magenta, yellow and black (CMYK) inks.
Profile : A file that contains enough information to let a CMS convert colors into or out of a specific color space. This may be a device’s color space, in which we will call it a device profile, with subcategories input profile, output profile, and display profile. Or an abstract color space such as a working space like Adobe RGB (1998).
Profile mismatch : The condition that arises when you open a file that contains an embedded profile other than the opening application’s assumed profile or working space.
Profiling : The act of creating a profile by measuring the current state of the device. Sometimes also known as characterization.
Quartz : Apple’s name for the display engine in Mac OS X.
Reflectance : ® The ratio of light shone onto a surface to the light reflected back to a detector. This is the measurement used by a reflection densitometer to compare density.
Reflective : Having the property of reflecting light off a surface. A sheet of paper and ink have reflective components.
Rendering intent : The setting that tells the color management system how to handle the issue of converting color between color spaces when going from a larger gamut to a smaller one. The ICC specifies four rendering intents: perceptual, saturation, and two types of colorimetric intents.
Retina : The layer of nerve cells lining the back of the eye and receptive to light.
RIP : Raster Image Processor. The RIP is either part of a digital printer or a separate computer attached to the printer. The job of the RIP is to convert the page image from vector form (usually expressed in PostScript) to the raster form needed by the marking engine of the printer. Some color-management processing and conversions can also happen in the RIP.
Saturation : The property of the light from a surface or light source by which we perceive the purity of the light – how much does the light contain photons of only a certain wavelength (highly saturated) or a mixture of many wavelengths (less saturated).
Saturation intent : The rendering intent that tries to preserve the saturation properties of colors as much as possible, even at the expense of hue accuracy of perceptual relationships. This is usually, but not always, the preferred rendering intent for information graphics such as graphs or maps, where it’s desirable to maintain saturated vivid colors, or where the saturation of different regions is designed to convey information.
Scanner metamerism : The type of metamerism where two color samples match to a human observer, but not to a certain scanner, or vice versa (the human does not see a match, but the scanner does).
Screen angle : In a halftone, the angle of the lines that form the halftone screen, relative to horizontal.
Screen frequency : In a halftone, the number of halftone cells, or lines per inch or centimeter.
Screening : In printing, the method used to simulate different tones and tints of ink by breaking the ink into dots of controlled size and frequency.
Simultaneous contrast : The effect where the perception of a color is affected by other colors seen simultaneously in the same field of view.
Smart monitor : A monitor with a direct connection to the host computer (rather than just an analog connection via the video card) that lets the computer control the monitor’s analog controls directly.
Soft-proofing : Using your monitor as a proofing device – displaying a simulation of how a document will appear when printed.
Source profile : In a color conversion, the profile that defines how to convert colors from the first color space to the profile connection space (PCS).
Space : (1) The final frontier. (2) In color and color management, shorthand for a color space. We often refer to the RGB space of a monitor, or the CMYK space of a printer, when referring to the specific definitions of the colors reproducible on that device in terms of its primaries.
Spectral data : A sampling of spectral power distribution, limited to the number of bands supported by the measurement device. Colorimetric and density data can be derived from spectral data.
Spectral power distribution : The amount of each wavelength contained in a sample of emitted or reflected light.
Spectrophotometer : A device for measuring the spectral properties of a surface- the degree to which the surface reflects light in different regions across the spectrum.
Spectrum : The full range of possible energy levels (wavelengths) of photons. The visible spectrum refers to the range of energy levels (wavelengths) visible to the eye.
Spi : Samples Per Inch. This is usually used when referring to the resolution of a digital camera, scanner, or a scan.
Spot color : A non-process color, usually based on a named color system, printed on a separate plate on a press.
sRGB : A standard default RGB color space intended for images on the internet.
Standard illuminant : One of the standardized list of illuminants defined by the CIE as representative of typical light sources. The best known of these are the A illuminant (incandescent bulb), and the D50 and D65 daylight illuminants.
Standard observer : The definition formalized by the CIE of the visual response of a typical human observer.
Stochastic screening : A form of FM screening.
Strip reader : An instrument designed to read a row or several rows of color patches at a time. You feed the target, in strips, into the instrument.
Subtractive primaries : Three pigments chosen that can reproduce other colors by the subtraction of wavelengths from white. One primary (cyan) subtracts long wavelengths, another (magenta) subtracts the medium wavelengths, and the other (yellow) subtracts the short wavelengths.
Successive contrast : The effect whereby the perception of a color is affected by other colors seen immediately before.
Tagging a document : The act of associating a source profile with an object. You can tag an object either by assigning a profile inside an application, or embedding a profile in the object as you save it to a file.
Target descriptor file : (TDF) A file, used for scanner and digital camera profiling, that contains the premeasured values for the color patches on a profiling target.
Tonal compression : The remapping of tonal values from a wide dynamic range to a narrower one. Often part of gamut compression.
Tone reproduction curve : (TRC) The graphed curve that describes the tone reproduction properties of a device. The graph shows the relationship between input values to the device and the resulting tone.
Total ink limit : The limit on the maximum amount of ink allowed at a time during four-color printing. If you allowed 100% of all four inks to get printed at a time, this would be a 400% coverage. As paper cannot hold this much ink, the limit is usually set well below 400%.
Transmissive : Having the property of transmitting light through a surface. Backlit media and the RGB color filter layer of an LCD display are transmissive.
Transmittance : (T) The ratio of light shone onto a surface to the light transmitted through to a detector. This is the measurement used by a transmission densitometer to compute density.
Trichromacy : The theory of color vision (now well verified by neurophysiology) that we have three types of photoreceptors, each responsive to different regions of the visible spectrum.
Tristimulus : Consisting of three stimuli. Used to describe measurements and experiments that ask a test subject to match a target stimulus by adjusting the intensities of three pre-chosen stimuli.
UCR : Under Color Removal. A method of black generation that uses black only in the neutral and gray areas.
Ultraviolet : (UV) The non-visible region of the electromagnetic spectrum just above the high energy, or violet, and of the visible spectrum.
UV brighteners : Additives used in papers, inks, and even detergents, to make whites look brighter by absorbing non-visible ultraviolet light and re-emitting visible light.
VideoLUT : The lookup table (LUT) located in the memory of a video card. The videoLUT is accessible by software on the computer, which can use it to convert all RGB values as they are sent to the monitor. This provides an easy way for software to control the overall gamma and white point characteristics of the video system.
Visual calibrator : Software used for monitor calibration that requires you to make visual judgments based on targets displayed on the screen, rather than exact measurements using a device.
Visible spectrum : That part of the spectrum containing the range of wavelengths visible to the eye, approximately 380-720 nanometers.
Wavelength : In a periodic wave, such as a light wave propagating through space, the distance from one wave crest to the next. Light wavelengths are measured in nanometers. The wavelength of a photon is related to its energy – the higher the energy, the shorter the wavelength.
White luminance : The luminance of the white point of a monitor.
White point : (1) The color (often described in terms of color temperature) and intensity (often measured as either luminance or density) of the brightest white reproducible by a device. For a printer, this is the color and brightness of the paper. For a monitor this is the color temperature and luminance of the monitor when displaying white, and can be modified. (2) The color (usually described in terms of color temperature) of a light source.
White point adaptation : The ability of the eye to adapt to a change in white point. This is related to the perceptual task of color constancy.
Working space : The color space chosen as the default space for documents of a certain mode. For example, in Adobe Photoshop an RGB working space is used as the default color space for new RGB documents, and a CMYK working space is used as the default for new CMYK documents. In most cases the best choice of working space is an editing space, but any bidirectional space can be used.
XY plotter : A rig used with a measurement instrument for measuring a page full of color patches. The instrument is mounted in the XY plotter, which can move the instrument precisely in horizontal or vertical position on the page.