[What is UCS (Uniform Color Space) ? / Color Story] NIPPON DENSHOKU INDUSTRIES CO.,LTD.

We have released the instruments with high accuracy which is useful for measuring the color and the light of materials. In this page, we introduce the basis of important information for measuring the color and the light including [preface of color story],[the three elements of color : hue - value - chroma], [munselll specification], [the recognition process of color], [the spectrum of light(spectrum distribution)], [the world of color for three-dimensional space of three stimulation value xyz], [what is ucs(uniform color space)], [example of color tolerance] and [unbalanced color judgement method]

Tri-stimulus values XYZ express the quantities of basic stimulus of color, however, these are difficult to use for color control in business enterprises. Therefore, for practical use, they are converted into a specification method corresponding to the three attributes of hue, lightness, and chroma. A space intended so that a color difference perceived as an equal dimension may correspond to an equal distance in the color space is called USC, and the dimension of color difference is expressed by the distance on this UCS coordinate.

		[Fig.9 : Lab* Color Specification System Three-Dimensional Sphere]

Like this, it is convenient for color control to convert a coordinate of tri-stimulus values to a coordinate that corresponds to color sense. Method of conversion are forth in JIS Z 8730 (color difference specification method), among which the most widely utilized is the L*a*b* color specification system. The defining equation of conversion is omitted here. The figure of a sphere on the left is what specifies color on the three-dimensional coordinate. And the L*a*b* color specification system chromaticity diagram (hue and chroma) is what expresses color on a horizontal section of a certain lightness. Therefore, the achromatic coordinate of that lightness is projected near the origin of a*=0, b*=0. With the center here, the color increases its lightness in spreading outwards. As seen above, a color coordinate that corresponds to perceived color is utilized for color control.

[Fig.9 : L*a*b* Color Specification System Chromaticity Diagram (Hue and Chroma)]

[Fig.10 : L*a*b* Color Specification System Chromaticity Diagram (Hue and Chroma)]