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256 colors

SmartNote: 2
Type: Term
ColorGeek factor: unrated
When a computer?s graphics system uses 8 bits of information to store each pixel in an image, the most effective way of gaining the widest range of colors is to use a Color Look Up Table (CLUT). This is called indexed color. Each pixel can be one of 256 colors (2^8) and the colors are chosen from a palette of 16 million. If the palette is chosen carefully and the image doesn?t have too wide a range of color, you can get a reasonably pleasing result. The choice of pallete, and what your operating system does to it, however can really mess up your images. Both the Mac OS and Windows have standard 256-color palettes (not that same colors of course). They are called the system palettes and were chosen to have the widest application possible. Photoshop can create custom palettes for your images but beware that the system displaying your image may not have access to the custom palette.

See Also

Term: Indexed Color
Term: Bit depth
Term: CLUT

Chroma

SmartNote: 20
Type: Term
ColorGeek factor: unrated
Chroma is the C component of the LCH color space.

Chroma represents how far out from the center of the color space (radially) a color lies. The farther out the more saturated the color.

The "colorfulness" of a sample judged proportional to the brightness of a white reference sample in the same medium and under the same illumination.

See Also

Term: LCH

Chromaticity Diagram

SmartNote: 21
Type: Term
ColorGeek factor: unrated
The Chromaticity Diagram is a horseshoe-shaped graph of the CIELab color space where the L component has been removed and the a and b components are then graphed in 2 dimensions. It is a very useful diagram for getting a quick feeling for not only the range of colors humans can perceive but the ranges of colors (gamuts) that different devices can (or cannot) display.

See Also

Term: CIELab, Lab

CIE - Commission Internationale De l'Eclairage

SmartNote: 22
Type: WebSite
ColorGeek factor:

Link: http://www.cie.co.at/cie/
(will open in a new browser window)

See Also

Term: CIELab, Lab
Term: CIExyY, xyY

CLUT

SmartNote: 26
Type: Term
ColorGeek factor: unrated
A CLUT is a Color Look Up Table. This is used with indexed color schemes when a lower number of bits are used to store each pixel's color so a look up table is used to increase the number of colors available. See Indexed Color for a more complete description.

See Also

Term: Indexed Color
Term: Bit depth

CMM - Color Matching Method

SmartNote: 27
Type: Term
ColorGeek factor: unrated
The CMM is the "engine" that actually does the work of color management. There are many different CMM's available from vendors such as Linocolor, Kodak, Adobe (within Photoshop), and others. The CMM contains the actual executable code that uses the ICC Profile information supplied by the user to transform the colors of a document.

While the debate may rage on about which CMM is best to use (and that probably differs the most depending on your workflow), one thing most color scientists would agree on is you should choose one CMM and use it throughout your workflow. At this time, in our opinion, this removes the Adobe CMM from most workflows as it is only available within Photoshop (and presumably more Adobe products as time goes on). Unless you do all your color work in one application, you should choose a CMM that is available to all applications.

See Also

Term: CMS Color Management System

CMYK Cyan, Magenta, Yellow, Black

SmartNote: 29
Type: Term
ColorGeek factor: unrated
The four colors commonly used in process color printing. Black is added to CMY to enhance the density of dark areas and solve gray balance problems encountered when trying to make neutral grays with CMY alone.

The letters stand for:

C: Cyan
M: Magenta
Y: Yellow
K: Key Color (which is usually black)

See Also

Term: Subtractive primaries
Term: Process color

CMY Cyan, Magenta, Yellow

SmartNote: 200
Type: Term
ColorGeek factor: unrated
The three "subtractive" primary colors used as the basis of all dye or pigment - based printing systems and color photography. A full range of colors including neutral grays and blacks can be produced with good CMY colorants (e.g. color film dyes) but typical printing inks are less than perfect.

Color Engine

SmartNote: 202
Type: Term
ColorGeek factor: unrated
A software utility running inside a RIP or application that applies links to images to create a mode change, e.g. from RGB to CMYK.

See CMM as an example

See Also

Term: CMM - Color Matching Method

Color Gamut

SmartNote: 203
Type: Term
ColorGeek factor: unrated
The specific range of colors seen by or reproduced by a device.

Color Management System

SmartNote: 204
Type: Term
ColorGeek factor: unrated
See CMS

See Also

Term: CMS Color Management System

Color Model

SmartNote: 205
Type: Term
ColorGeek factor: unrated
A mathematical way of predicting the behavior of human vision or color devices (see Color Space)

Color Space

SmartNote: 206
Type: Term
ColorGeek factor: unrated
A description of the range of visible colors in standardized numerical terms. As human vision is based on three types of light sensor ("red", "green" and "blue" cones) color spaces are usually "3-dimensional".

Colorimetric

SmartNote: 209
Type: Term
ColorGeek factor: unrated
Measured or expressed in tristimulus terms, such as XYZ.

Colortron

SmartNote: 211
Type: Term
ColorGeek factor: unrated
A spectrophotometer from Light Source Technologies capable of measuring reflection and transmission samples as well as color monitors. (Lightsource is owned by X-Rite)

CRD Color Rendering Dictionary

SmartNote: 212
Type: Term
ColorGeek factor: unrated
A table that can be downloaded to a PostScript Level II RIP to control color transformations handled by PostScript. CRD?s gan often be generated by the same software that produces ICC Profiles.

See Also

Term: Postscript
Term: Profile

Delta E (dE)

SmartNote: 213
Type: Term
ColorGeek factor: unrated
A measurement of "color error", or "color difference" based on L*a*b* coordinates. A dE of 1.0 is a just- perceptible difference. A dE of 4 to 7 is the typical limit of acceptable error in commercial reproduction, but the limit varies in different color regions and applications.

Density

SmartNote: 214
Type: Term
ColorGeek factor: unrated
A measure of darkness or amount of color used widely in photography and printing. The logarithm to base 10 of the reciprocal of fractional transmittance or reflection.

See Also

Term: Reflectance
Term: Opacity

Device-Dependent Color

SmartNote: 215
Type: Term
ColorGeek factor: unrated
Measuring and "profiling" input and output devices in terms specific to each device. A scanner's RGB values have no simple relationship to a printer's CMYK values for the same color because both values are device-dependent.

Device-Independent Color

SmartNote: 216
Type: Term
ColorGeek factor: unrated
(1) The concept of automatically good color reproduction of an image from any source on any destination device. (2) Measuring and "profiling" input and output devices in terms that are independent of their native color spaces. (3) An intermediate color space to which scanners and printers are calibrated and through which images are translated from one device to another.

Digital Swatchbook

SmartNote: 217
Type: Term
ColorGeek factor: unrated
A spectrophotometer from X-Rite Corporation. It is a hand-held device which is good for taking readings of anything you may have at hand. If you are reading many patches, as when creating a printer profile, you may want a more automated solution like the DTP41 strip-reading spectrophotometer or the GretagMacbeth Spectrolino / Spectroscan combination which combines a spectrophotometer with an automated x-y reading table.

Gamma

SmartNote: 221
Type: Term
ColorGeek factor: unrated
A non-standardized measure of contrast for color scanners, video monitors and photographic materials. A gamma of 1.0 usually means normal or no change in contrast, except in Macintosh monitors where gamma 1.8 is standard. Higher gamma numbers usually mean more contrast with darker mid-tones. Lower gamma numbers usually mean lower contrast and lighter mid-tones. Gamma pivots on (does not change) the white and black point of an image. Gamma is typically applied by raising fractional L*, fractional RGB or fractional XYZ to the power of gamma.

See Also

Term: Curves, tone curves

Gamut Compression

SmartNote: 223
Type: Term
ColorGeek factor: unrated
A form of gamut mapping in which the range of color values produced by an input device (e.g. a color scanner) is reduced to fit within the smaller available gamut of the output device (e.g. a CMYK press). Gamut compression can be crucial to good color reproduction but colors that have been gamut compressed will seldom match the original.

Gamut Mapping

SmartNote: 224
Type: Term
ColorGeek factor: unrated
The redistribution of color values from an input device (e.g. color scanner or printer) to fit the smaller or larger gamut of the output device. If the input gamut is larger than the output gamut, gamut mapping is the same as Gamut Compression. If the input gamut is smaller than the output gamut, colors and contrast can be intensified through Gamut Expansion, or colors can be mapped to their exact equivalents, e.g. for digital proofing.

GCR Gray Component Replacement

SmartNote: 225
Type: Term
ColorGeek factor: unrated
The replacement of some or all of the CMY inks in a CMYK pixel with enough black ink to restore the pixel to the same visual appearance. (see UCA, UCR).

See Also

Term: Process color
Term: Color Separations
Term: Profiling

Gradation Control

SmartNote: 226
Type: Term
ColorGeek factor: unrated
A means of adjusting tonal contrast of specific tonal regions, either equally for all colorants or imaging channels, or separately for independent channels.

Gradation

SmartNote: 227
Type: Term
ColorGeek factor: unrated
The relationship of reproduced lightness values to original lightness values in an imaging process, usually expressed as a "tone curve".

Hi-Fi Color

SmartNote: 228
Type: Term
ColorGeek factor: unrated
Any process that increases the color gamut of an output imaging device (printer). Usually refers to adding extra inks and plates to the traditional CMYK set to improve the color gamut of offset lithography. The three main Hi-Fi methods are; the Küppers approach (CMYK+RGB), Pantone(r) Hexachrome? (CMYK + Orange & Green) and MaxCMY (CMYK + extra CMY).

See Also

Term: Pantone Colors
Term: N-color

ICC International Color Consortium

SmartNote: 231
Type: Term
ColorGeek factor: unrated
An international group that has proposed open, cross-platform standards for the description and handling of device-independent color.

See Also

Term: Profile

IT8.7/1

SmartNote: 232
Type: Term
ColorGeek factor: unrated
An ISO standard transmissive color target available from all major color film manufacturers. CIE data provided with each copy of the target enable scanning devices to be characterized or "profiled" in CIE terms.

See Also

Term: IT8.7/2

IT8.7/2

SmartNote: 233
Type: Term
ColorGeek factor: unrated
A reflective version of the IT8.7/1 provided with its own CIE data.

See Also

Term: IT8.7/1

Kelvin

SmartNote: 234
Type: Term
ColorGeek factor: unrated
An absolute temperature scale used in scientific circles. The "color temperature" of a light source, monitor or image area, defined in "degrees Kelvin" (°K), is the temperature a perfectly black radiating object would be if it glowed that shade of white. Average daylight is standardized at 6500°K (Europe) and 5000°K (North America). Higher temperatures are bluer, lower temperatures are redder.

Lightness

SmartNote: 235
Type: Term
ColorGeek factor: unrated
The brightness of an area expressed relative to the whitest area in the viewer's field of vision or the brightest white the device is capable of seeing or producing.

Linearization

SmartNote: 236
Type: Term
ColorGeek factor: unrated
The process of measuring and correcting for a device's inability to see or reproduce a straight line of tones from black to white. Most commonly used to ensure an image setter reproduces the same halftone dot values predicted by the imaging software. Linearization

Link

SmartNote: 237
Type: Term
ColorGeek factor: unrated
Combining an input profile with an output profile produces a mathematical look-up-table (LUT) that translates colors from an input device into the best available matching colors on the output device. Changes or edits can be combined in the link to alter or improve the image.

Metamerism

SmartNote: 238
Type: Term
ColorGeek factor: unrated
The phenomenon by which two materials that match under one circumstance appear different to different viewers or under different lighting. Metameric mismatch occurs when tristimulus values are the same but spectral characteristics are not.

See Also

Term: Spectrophotometer
Term: Colorimeter

Mode Change

SmartNote: 239
Type: Term
ColorGeek factor: unrated
Transformation of an image from one mode to another, e.g. RGB to CMYK.

Output Target

SmartNote: 240
Type: Term
ColorGeek factor: unrated
A series of color patches sampling the full range of output device colorant combinations. When printed and measured the resulting CIE values are tabulated with the colorant combinations that produced them to create the output profile.

Patch

SmartNote: 241
Type: Term
ColorGeek factor: unrated
A single color sample in an input or output target.

Plug-ins

SmartNote: 242
Type: Term
ColorGeek factor: unrated
A third-party filter or sub-program that works within a host application such as Adobe Photoshop(r).

Postscript

SmartNote: 243
Type: Term
ColorGeek factor: unrated
The most common page description language, invented by Adobe and used almost universally in desktop publishing. Postscript code tells the RIP how to construct page elements such as text or linework and indicates the scale, rotation and cropping of continuous tone images.

PPD Postscript Printer Description

SmartNote: 244
Type: Term
ColorGeek factor: unrated
A file located in the System Folder and accessible to any printing application, describing the features and capabilities of a printer.

Printing Technology

SmartNote: 245
Type: Term
ColorGeek factor: unrated
A type of printing method, e.g. offset lithography, ink jet, dye-sublimation, etc.

Reference

SmartNote: 247
Type: Term
ColorGeek factor: unrated
A standard against which others are measured.

Relative Colorimetry

SmartNote: 248
Type: Term
ColorGeek factor: unrated
Colorimetric measurements expressed relative to the white point of the device or image, rather than as "absolute" CIE values. In relative colorimetry, the white point would be 100 X, 100 Y, 100 Z.

Relative Densitometry

SmartNote: 249
Type: Term
ColorGeek factor: unrated
Densities expressed relative to the white point of the image or device. Relative reflection densities have the white paper density subtracted. Relative transmission densities have the clear film base subtracted.

RIP Raster Image Processor

SmartNote: 251
Type: Term
ColorGeek factor: unrated
A software or hardware mechanism that converts page description data such as Postscript code into lines (rasters) of micro-image units (pixels or microdots) that are arranged for high-speed sequential output to the imagesetter.

SCID Images Standard Color Image Data

SmartNote: 253
Type: Term
ColorGeek factor: unrated
Eight standard images representing difficult reproduction challenges.

Serial Port

SmartNote: 254
Type: Term
ColorGeek factor: unrated
A connection for computer peripherals. The Macintosh has two serial ports, one marked with a modem (phone) symbol and one with a printer symbol. Serial devices like colorimeters can usually be connected to either port.

Transformation

SmartNote: 256
Type: Term
ColorGeek factor: unrated
The process of transforming an image from one color space or color mode to another, usually through a Link or Color Table.