Lab color space

The Hunter Lab color space is organized in a rather simple way (Fig. 16.2). The L axis, as lightness, runs from top to bottom. The maximum for L is 100, the absolute... 

Figure 16.2 The Hunter Lab color space in a cube form. It is based on the Opponent-Colors...

TABLE 16.11 Shift of lightness (L in Hunter Lab color space) for an extruded (as is and planed) and injection-molded wood flour (50% w/w, 40 mesh)-filled HDPE (MFI 0.72)... 

Hunter Lab color space, 586, 587 Hydrated alumina, 80 Hydrogen atoms in polyethylene, 497 Hydrogen bonds, 162 Hydroperoxide RjOOH, 497-498 Hygroscopicity, 63, 128 Hygrothermal test, 407 Hyphae, 413... 

Figure 16.2 The Hunter Lab color space in a cube form. It is based on the Opponent-Colors Theory. The theory assumes that the human eye perceive color as pairs of opposites, namely, light-dark, red-green, yellow-blue (with HunterLab permission).

Figure 2 UV stability of reactor blend polypropylene copolymer plaques. (Delta L refers to the change in the L components of the LAB color space co-ordinates. KLY = 1 kcal/cm 4.18cal = 1J).

Color Difference Evaluation. Shade evaluation is comparable in importance to relative strength evaluation for dyes. This is of interest to both dye manufacturer and dye user for purposes of quaUty control. Objective evaluation of color differences is desirable because of the well-known variabihty of observers. A considerable number of color difference formulas that intend to transform the visually nonuniform International Commission on Illumination (CIE) tristimulus color space into a visually uniform space have been proposed over the years. Although many of them have proven to be of considerable practical value (Hunter Lab formula, Friele-MacAdam-Chickering (FMC) formula, Adams-Nickerson formula, etc), none has been found to be satisfactorily accurate for small color difference evaluation. Correlation coefficients for the correlation between average visually determined color difference values and those based on measurement and calculation with a formula are typically of a magnitude of approximately 0.7 or below. In the interest of uniformity of international usage, the CIE has proposed two color difference formulas (CIELAB and CIELUV) one of which (CIELAB) is particularly suitable for appHcation on textiles (see Color). 

Figure 6-10 The Hunter L, a, b Color Space. Source From Hunter Associates Lab., Inc.

Subsequent to determining standard and lot tristimulus XYZ values, one simply plugs those calculated values into the CIE Lab color equations. Why the CIE system Because CMC uses the DLab values, generated in CIE color space, to determine DC, DH, and eventually CMC DE. 

CIELAB An internationally accepted color space. CIE stands for Conjxnission Internationale de FEclairage. LAB stands for coordinates 1, a, and b, which are defined as mathematical coordinates in the three-dimensional color space. (Billmeyer, F. W. Saltzman, M. Principles of Color Technology , 2nd ed. Wiley New York, 1981 Chap. 2.)... 

Note that the uniformity of a color space is of concern only if color is regarded as a (visual) quality. When using color as an analytical tool, the color system which differentiates the iron oxides most effectively would be the most favorable, no matter whether it is uniform or not. A discriminant analysis performed with a large number of iron oxide samples showed that CIE-Yxy, CIE-Lab, and the Munsell system performed equally well (Scheinost and Schwertmann, 1999). Therefore, the choice of a color system is not crucial. Furthermore, computer programs are available which transfer colors from one system into another. More details on color theory and color systems are given by Wyszecki and Styles (1982) and Hunter and Harold (1987). 

The near-linear nature of (Lab), CIELUV, and CIE-LAB spaces make color difference calculation more meaningful through the whole of color space. More sophisticated equations yielding greater precision have been developed for specific industrial applications. 

Figure 12.1 Chromatic parameters (<3 6 plane of the CIE Lab coordinates) of oxide (a) and non-oxide (b) perovskites proposed as pigments. The numbered fields represent the color space of industrial Inorganic pigments black Fe-Cr-Co-Ni spinel (1), magenta Cr-malayaite (2), pink hematite-zircon (3),...

The LAB color is designed to approximate human vision. The RGB or CMYK spaces model the output of physical devices rather than human visual perception [7]. The transformations among the color modes may be done with the help of appropriate editing applications or color management software which convert color data to different color standards (RGB, CMYK, L a b etc.) [8]. 

Margulis D. Photoshop Lab Color (2006) The Canyon Conundrum and Other Adventures in the Most Powerful Color space. Berkeley, Calif. London Peachpit Pearson Education... 

As an initial (demonstration) application of the Icon/1000 control system, we automated two simultaneous acrylic lab polymerizations. In this application, heaters, agitators, and metering pumps are controlled. A batch proceeds automatically from state to state unless the operator intervenes through one of a series of color CRT touch screens allowing him to take complete manual control of the batch for as long as he desires. All important process variables are continually monitored and recorded. The entire control scheme was created, tested, and modified several times in the space of two months, without formal instruction, by a chemical engineer with little previous programming experience and no previous experience at all with this system. 

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