Nearly all color management software today uses a device-independent space defined by the Commission International de l' éclairage (CIE) in 1931. This space aims to describe all colors visible to the human eye based upon the average response from a set of people with no vision problems (termed a "standard colorimetric ").The CIE space of visible color is expressed in several common forms: CIE xyz (1931), CIE LAB, and CIE L u'v' (1976). Each contains the same colors, however they differ in how they distribute color onto a two-dimensional space:
(All color spaces shown are 2D cross-sections at 50% Luminance)
CIE xyz is based on a direct graph of the signals from each of the three types of color sensors in the human eye. These are also referred to as the X, Y and Z tristimulus functions (that were created in 1931). However, this representation allocates too much area to the greens — confining most of the apparent color variation to a small area.
CIE L u'v' was created to correct for the CIE xyz distortion by distributing colors roughly proportional to their perceived color difference. A region that is twice as large in u'v' will therefore also appear to have twice the color diversity — making it far more useful for visualizing and comparing different color spaces.
CIE L*a*b* remaps the visible colors so that they extend equally on two axes — conveniently filling a square. Each axis in the LAB color space also represents an easily recognizable property of color, such as the red-green and blue-yellow shifts .These traits make LAB a useful color space for editing digital images, such as with Adobe Photoshop, Lightroom, etc.
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