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CIELab, Lab

SmartNote: 19
Type: Term
ColorGeek factor:
CIELab is the color space that ICC Profiles and CMMs often use as an intermediary space when converting colors. So a monitor to printer match translates colors from the monitor*s space (RGB) into Lab and then into the printer*s color space (CMYK for example).

The L component is the lightness of the color.
The a component is the red/green scale (+a is red, -a is green)
The b component is the blue/yellow scale (+b is yellow, -b is blue - go figure)

CIELab, or more correctly CIEL*a*b* is a (mostly) device independent color-space based on the measurements of hundreds of humans the CIE made in 1931 when they created the CIEXYZ color space. In 1976 the CIE created the Lab space to reflect the entire gamut or range of colors the human eye can typically see. The Lab space, unlike other CIE color spaces, is supposed to be perceptually uniform. That is, any movement within the space, in any direction, should result in an equally perceptible color shift. There are many who believe that the Lab space is not perceptually uniform but that is outside the scope of this glossary.

LCH is another way of measuring the same color space. (see LCH for more information)

The Lab color space is not precisely device independant as it is defined relative to a reference white point. This white point is often based on the whitest point that can be generated by a device or a standard white point (like D50).

See Also

WebSite: CIE - Commission Internationale De l'Eclairage
Term: CIExyY, xyY
Term: LCH

Chromaticity

SmartNote: 194
Type: Term
ColorGeek factor: unrated
The color properties of a sample judged independently of luminance, i.e. in terms of hue and saturation only.

CIE Committee Internationale de l'Eclairage (The International Commission on Lighting)

SmartNote: 195
Type: Term
ColorGeek factor: unrated
The body responsible for recommendations on photometry and colorimetry. The CIE has defined several "color spaces" that describe the range of visible colors in unambiguous numerical terms.

CIEXYZ, XYZ

SmartNote: 196
Type: Term
ColorGeek factor: unrated
A CIE color space defined in the three dimensions; X, Y and Z. The XYZ coordinates are "matching functions" which represent the amounts of theoretical red, green and blue lights necessary to reproduce a certain color.

CMS Color Management System

SmartNote: 199
Type: Term
ColorGeek factor: unrated
A means of controlling color reproduction based on independent calibration of input and output devices and custom or automated "gamut mapping" between devices. CMS components typically include software applications (such as Matchbox Profiler and ColorBlind edit), system-level utilities such as Apple's ColorSync 2.0 (which utilize CMM's) and standardized device description formats such as ICC "profiles".

See Also

Term: CMM - Color Matching Method
Utility: ColorSync