Color systems

A color can be numerically defined as a point in a three-dimensional color space. In the past, a vast number of color spaces, optimized for different applications have been developed. The most physical of these is the CIE-Yxy space, where all colors lie within a plane resembling a shoe sole. An arbitrary point B within that plane is defined by the Cartesian coordinates x and y, where the redness increases with x, and the greenness increases with y. The lightness, Y, is perpendicular to x and y out of the plane. An alternative 

Equal Euclidean distances in the CIE-Yxy system are not necessarily perceived by a human observer as equal color distances. To match Euclidean and perceived distances, a wide variety of so-called uniform color spaces has been developed (Hunter and Harold, 1987). One of the first of these uniform systems was developed in the early 1900 s by the artist A.H. Munsell. Starting with the observation that brighter hues like yellow and red create a much stronger color sensation at color saturation than darker hues like blue or green, he mounted color chips on a rotating Maxwell disk to 

In contrast to the patchwork-like Munsell system, the CIE system and its modifications (developed by the International Commission on Illumination, CIE, in 1931) create numerically continuous color spaces. They are based on the principle of tricliromaticity of vision which states that the 

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). 

4 Identification of Iron Oxides by Color and Crystal-Field Bands 

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Measurement of Whiteness. The Ciba-Geigy Plastic White Scale is effective in the visual assessment of white effects (79), but the availabihty of this scale is limited. Most evaluations are carried out (ca 1993) by instmmental measurements, utilising the GIF chromaticity coordinates or the Hunter Uniform Color System (see Color). Spectrophotometers and colorimeters designed to measure fluorescent samples must have reversed optics, ie, the sample is illuminated by a polychromatic source and the reflected light passes through the analy2er to the detector. 

Blt-M ppedImages. A bit map is a grid pattern composed of tiny cells or picture elements called pixels. Each pixel has two attributes a location and a value or set of values. Location is defined as the address of the cell in a Cartesian, ie, x andjy coordinate, system. Value is defined as the color of the pixel in a specified color system. Geometric quaUties of images are a function of the location attribute, ie, the finer the grid pattern, the more precisely can the geometric quaUties be controlled. Color quaUties are a function of the value attribute, ie, the more bytes of computer memory assigned to describe each pixel, the more precisely can the color quaUties be controlled. 

Thermal printing usually involves passing materials over a full-width array of electronically controlled heaters (a thermal printhead). This marks thousands of spots simultaneously, so pages print relatively quickly. Image data to control the printhead usually come from computer systems. Black-and-white and full-color systems are both practical. Color is slower and more cosdy to purchase and use, primarily because this involves three or four successive printing operations, one for each color used. 

Other Color Order Systems. The Natural Color System (24), abbreviated NCS, developed ia Sweden is an outgrowth of the Hesselgren Color Adas, and uses the opponent color approach. Here colors are described on the basis of their resemblances to the basic color pairs red-green and blue-yeUow, and the amounts of black and white present, all evaluated as percentages. Consider a color that has 10% whiteness, 50% blackness, 20% yellowness, and 20% redness note that the sum is 100%. The overall NCS designation of this color is 50, 40, Y50R iadicating ia sequence the blackness, the chromaticness (20 + 20), and the hue (50% on the way from yellow to red the sequence used is Y, R, G, B, Y). 

This transformation results in a three-dimensional space that follows the opponent color system with +a as red, —a as green, +5 as yellow, and — b as blue. CIELAB is closely related to the older Adams-Nickerson, modified Adams-Nickerson, and other spaces of the Y,a,b type, which it replaced (1,3). 

E. Jacobson, Basic Color. An Interpretation of the Ostwald Color System, P. Theobald, Chicago, lU., 1948. 

Nevertheless, it is well to note that it was the subjective observation of the lack of correction for luminosity in the Munsell System that gave impetus to the development of the CIE Color System. The major problem vidth the Munsell system was that each person attempting to match colors did not produce the exact same result. So color matching became dependent upon the person. 

Fujikawa K, Ryo H, Kondo S. 1985. The Drosophila reversion assay using the unstable zeste-white somatic eye color system. In Ashby J, de Serres FJ, et al., eds. Progress in mutation research. Vol. 5. Evaluation of short-term tests for carcinogens. Amsterdam, The Netherlands Elsevier Science Publishers, 319-324. 

CIE color system, 7 304. See also Commission Internationale de l clairage (CIE) chromacity diagrams, 7 313-315 standard illuminants, 7 315-316 CIEDE200 color difference equation, 7 322 CIELAB, 7 304 CIELAB Color Space, 7 320 CIELAB color values, of flax fiber, 11 614t Cielab dye nomenclature system, 9 244 CIELAB Metric Color Spaces, 7 320 CIELAB system, 19 428, 451 CIELUV Color Space, 7 319-320 CIE Standard Observer, 7 311-312 Cigarette filters... 

Commission Internationale de l Eclairage (CIE) standards, 19 585. See also CIE color system... 

ISCC-NBS Centroid (color) system, 7 310 I-section rayon, 11 262, 263 Ishizuka multipolar cell, 15 337 ISIS, 6 11 Ismelin Sulfate... 

KOH plants, environmental awareness in, 20 634. See also Potassium hydroxide KOH solution, 12 215 meta-Koksowy coal grade (Poland), 6 713t Kolbe-Schmidt reaction, 2 208 of salicylic acid synthesis, 22 7-8 Kolmogoroff microscale, 16 697 Konica Dry Color System, 19 348 Konjac glucomannan, 4 7241... 

Natural antioxidants, 12 60-61 Natural attenuation, defined, 3 759t Natural boric acid, 4 133t Natural cements, 5 502 Natural colors, 12 51 Natural color system (NCS), 7 309 Natural convection, 13 245 Natural defenses, against silver, 22 655, 681... 

Osteoporosis biomarkers, 17 649 Ostromislensky, Ivan, 25 628 Ostwald color system, 7 309 Ostwald glass capillary viscometer, 21 728 Ostwald ripening, 10 124... 

Colors specified in terms of the tristimulus values X, Y, and Z are fairly hard to visualize. For this and other reasons, a variety of different color systems have been devised. The color coordinates in these systems can be calculated from the X, Y, and Z values, which are of central importance to color measurement because of their close link to measurable quantities. 

According to ASTM D 2805-70, the hiding power of a layer is characterized by the ratio of the Y values (as defined in the CIE color system) over a black and a white patch of substrate. If this ratio is larger than 0.98, the layer is referred to as hiding. This criterion occasionally fails if applied to brightly colored pigments. 

There are several techniques which determine the hiding power of a pigmented medium for practical application. Colored systems are typically tested by measuring their ability to entirely cover up a standard black and white checkerboard substrate. Parameters used as variables are the pigment concentration and/or the... 

Color is determined by reflectance and can be determined by using a colorimeter based on the CIE color system. This method expresses the brightness as Color L, the absorption at the green-red axis as Color a and the yellowness as Color b along the blue-yellow axis of this color coordination system. 

Where releases of flammable or toxic chemicals are possible, a flammable or toxic gas alarm system is often established as part of the plant emergency alarm system. Best practices require different types of alarms to be annunciated differently, both audibly and visually. For example, the toxic alarm stations may be provided with a blue light to distinguish them from fire alarm stations that are red. A consistent color system for lights should be adopted. 

In terms of sensitivity, the detection limits on the microarray slide using the tw o-color system approached 0.1 ng/mL for antigen arrays and 1 ng/mL for antibody arrays. Both were able to measure specific proteins in mixtures at 1 part per million in total protein (partial concentration). 

Very interesting method of template polymerization was proposed by Japanese scientists. The method is based on the charge transfer interaction between template and monomer. In the course of the studies on the interaction of poly(maleic anhydride) with organic amines, the authors found strong charge transfer interaction of pyridines with poly(maleic anhydride). The polymer with pyridine gives brown-colored system with the absorption maximum at 480 nm. 

There were old and new color systems for marking the Army projectiles, and they are briefly explained on pp 266—69 of Ref 3 The following abbrns are used in this Section on AMMUNITION ... 

Vogel, E.W. (1985) The Drosophila somatic recombination and mutation assay (SRM) using the white-coral somatic eye color system. Prog. Mutat. Res., 5, 313-317 Warns, T.J. (1987) Diethylhexylphthalate as an enviromnental contaminant—a review. Sci. total Environ., 66, 1-16... 

The key component of the optical recording system is the recording medium, which is marked in one step and read in another step with a laser beam. Many materials have been considered for the purpose, including metal-films, organic dyes, dye-loaded polymers, metal-loaded polymers, discontinuous metal films, thermal coloration systems and bilayers (1-19). Tellurium- and gold-based optical disks have been the most widely studied materials to date. 

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