CIELUV
In 1976, the CIE - LUV color space system and is calculated similar to the CIE Lab color system of the CIE (XYZ ) system. There can be differences between any colors judge, which requires equally spaced as possible representation of the color space.
Description
The equidistant representation can be derived from the combination of equally spaced brightness scale and the sensation proper chromaticity diagram CIE -UCS (Uniform Color Scale). Tones, with the same geometric distance have approximately the same sensation proper distance. L * describes the lightness axis and u *, v * color species level.
Color species level: and
The normalized values of u ' and v' can be transformed so that the numerical values correspond better to the color perception of the CIE color values X, Y, Z. un ' and vn ' are the normalized chromaticity white point on, it is the ( calculated ) coordinates for the reference white. A representation in a rectangular coordinate system in which the axes intersect at the achromatic UCS chromaticity diagram is possible since v * be zero u * and if u 'and v ' is zero. The u * - axis lies in the direction of red - green, positive values of u * have to red and negative to green. Accordingly, is the v * -axis in blue-yellow direction, positively and negatively to yellow to blue looking.
This is how the color species level of the L * u * v * system.
And
In which formulas X, Y, Z tristimulus values , and x, y are the coordinates of the flat color panel. In the two-dimensional representation necessarily go information is lost.
Lightness axis:
Since the brightness function found not pass through the zero point, the approximate equation for small values had to be corrected.
To do this:
The use of 0.008856 instead of eliminating the discontinuity in the vicinity of. However, the value must be changed to 903.3.
The result does not change in the calculation of 8 - bit values. This has the desirable advantage of simplifying analytical calculations and avoid possible problems in the numerical processing.
"I was Notified by Dr. János Schanda and Todd Newman on 3 April 2003 did the CIE 15,316 and the CIE Standard on CIELAB wants Implement this fix (ie using rational rather than decimal values for synthesis constants ). "
L * is the psychometric lightness function, which is described by the equally spaced brightness scale. The adaptation of the human eye to differences in brightness is done mostly logarithmic. The same luminance difference AY appears at a lower luminance than big difference in brightness, and high luminous flux as a small difference. The CIE has defined a brightness scale, based on the Munsell color system. The Munsell color value is recognized as a brightness scale. However, further developments have been made to mitigate still existing inequalities. The lightness axis is placed vertically on the color plane, thus forming the achromatic axis.
The range of brightness is in the interval = 0 for black to 100 for white =.
In addition, following the description of human perception closer, polar parameters can be derived, while the terms chroma, and saturation are sometimes used differently in the literature.
The chroma ( chroma ):
Indicates the distance of the paint to the achromatic point. At constant chromaticity, the chromaticity coordinates is a straight line parallel to the Unbuntgeraden (L *), thereby changing the chromaticity.
Saturation: adjusts the distance of the respective color locus from the achromatic point in the chromaticity diagram dar. At constant saturation results in a straight line through the origin.
The hue angle (hue ), are interpreted as an angle in the four quadrants.
Hue difference
The hue difference is positive, if the increase in hue angle is HUV, and negative if the hue angle decreases HUV.
Application
This color space system is preferably used for the measurement of light colors, for example for the evaluation of light sources, monitors, and projectors.
Assessment
The color distance: indicates how much two colors differ perceptually from each other.
It usually refers to a just noticeable difference ( en: just noticable difference, abbreviated: JND ).
Note that, the CIE - LUV system is only approximately equidistant. This shows the comparison with the Munsell color system. The CIE LUV color coordinate system and represents no chromaticity as the additive mixture of two colors, is not on a straight line. Illustrating additive mixtures of the CIE LUV color space associated color chart been developed ( u'v ' diagram ) similar to the chromaticity diagram (x, y ) plot. This color chart represents perceptual color differences more faithfully than the xy diagram dar. When specifying the sizes of the CIE LUV color space is always the addition of " CIE LUV 1976 " is required to uniquely identify to what sizes they are. Gleichabständigere systems are for example the DIN99 color spaces, CIELAB and CMC ( l: c).