# lab color space range

Defined by the Commission Internationale de l’Eclairage (CIE), the L*a*b* color space was modeled after a color-opponent theory stating that two colors cannot be red and green at the same time or yellow and blue at the same time. Delta, the fourth letter of the Greek alphabet and symbolized as a triangle, is used in science to indicate difference. The Wide Gamut color space is an expanded version of the Adobe RGB color space, developed in 1998. Delta E is the difference between two colours designated as two points in the Lab colour space. CIELAB values range as follows: L lies between 0 and 100, and a and b lie between -110 and 110. Colors in the L*a*b* color space can exist outside the RGB gamut (the valid set of RGB colors). The Lab Color mode has a lightness component (L) that can range from 0 to 100. Color management systems use Lab as a color reference to predictably transform a color from one color space to another color space. It is usual to represent the gamut of a colour reproduction system graphically as the range of colours available in some device independent colour space. As a comparison, the Adobe Wide Gamut RGB color space encompasses 77.6% of the visible colors specified by the Lab color space, whilst the standard Adobe RGB color space covers just 50.6%. If you have skin color, then you have a boomerang shaped gamut and no simple thresholding in any color space will get it. If, on the other hand, I like "normal" colours, not especially saturated, the sRGB or REC 709 will do very well ! Often the gamut will be represented in only two Output from Lab2RGB is always between 0 and 1. Delta E is the difference between two colours designated as two points in the Lab colour space. A good color space is the space I need for my photo ! Figure 4.7 Lab Colour Space. YIQ Color Space 17 R´ = Y + 1.140V G´ = Y – 0.395U – 0.581V B´ = Y + 2.032U For digital R´G´B´ values with a range of 0– 255, Y has a range of 0–255, U a range of 0 to These routines convert images back and forth from RGB to CIELAB color spaces. Delta, the fourth letter of the Greek alphabet and symbolized as a triangle, is used in science to indicate difference. Identifying Color Differences Using CIE L*a*b* Coordinates. A matrix RGB color space is also defined in terms of its Tone Response Curve ("TRC" for short). A colour gamut is the area enclosed by a colour space in three dimensions. If I photograph, film or work with very saturated colours, for example with the HDR technique, I need so-called wide gamut spaces (larger than the sRGB like the ProPhoto). Commission Internationale de l’Eclairage (CIE), a non-profit organization considered to be the authority on the science of light and color, has defined color spaces, including CIE XYZ, CIE L*a*b*, and CIE L*C*h, for communicating and expressing object color. A color space can be described as a method for expressing the color of an object using some kind of notation, such as numbers. RGB values may be in the range from 0 to 255, or from 0 to 1. A matrix RGB color space is defined in terms of the location of its RGB primaries in the XYZ reference color space, which in turn determines its respective size (volume) and shape in the LAB reference color space. The L*a*b* color space provides a more perceptually uniform color space than the XYZ model. Follows: L lies between 0 and 100, and a and b lie between -110 110! Matrix RGB color space than the XYZ model values may be in the Lab color mode has lightness! 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