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The Abney effect describes the perceived hue shift that occurs when white light is added to a monochromatic light source.〔Pridmore, R. “Effect of purity on hue (Abney effect) in various conditions.” ''Color Research and Application.'' 32.1 (2007): 25–39.〕 The addition of white light will cause a desaturation of the monochromatic source, as perceived by the human eye. However, a less intuitive effect of the white light addition that is perceived by the human eye is the change in the apparent hue. This hue shift is physiological rather than physical in nature. This variance of hue as a result of the addition of white light was first described by the English chemist and physicist Sir William de Wiveleslie Abney in 1909, although the date is commonly reported as 1910. A white light source is created by the combination of red light, blue light, and green light. Sir Abney demonstrated that the cause of the apparent change in hue was the red light and green light that comprise this light source, and the blue light component of white light had no contribution to the Abney effect.〔W. de W. Abney. “On the Change in Hue of Spectrum Colours by Dilution with White Light.” ''Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character.'' 83.560 (1909): 120–127.〕 == Chromaticity diagrams == Chromaticity diagrams are two-dimensional diagrams that plot the projection of the International Commission on Illumination (CIE) XYZ color space onto the (x, y) plane. The X, Y, Z values (or tristimulus values) are simply used as weightings to create new colors from the primary colors, much in the same way that RGB is used for creating colors from primaries in televisions or photographs. The x and y values used to create the chromaticity diagram are created from the XYZ values by dividing X and Y by the sum of X, Y, Z. The chromaticity values that can then be plotted are dependent upon two values: dominant wavelength and saturation. Since luminous energy is not included, colors that differ only in its lightness are not distinguished on the diagram. For instance, brown, which is just a low-luminance mixture of orange and red, will not appear as such.〔(Introduction to Chromaticity Diagrams and Color Gamuts )〕 The Abney effect can be illustrated on chromaticity diagrams as well. If one adds white light to a monochromatic light, one will obtain a straight line on the chromaticity diagram. We might imagine that the colors along such a line are all perceived as having the same hue. In reality, this does not hold true, and a hue shift is perceived. Correspondingly, if we plot colors that are perceived as having the same hue (and only differing in purity) we will obtain a curved line. In chromaticity diagrams, a line that has constant perceived hue must be curved, so that the Abney effect is accounted for.〔Widdel H., Lucien D. ''Color in Electronic Displays''. Springer (1992): 21–23.〕 The chromaticity diagrams that have been corrected for the Abney effect are therefore excellent illustrations of the non-linear nature of the visual system.〔K. Mantere, J. Parkkinen, and T. Jaaskelainen. “Simulation of white-light adaptation characteristics with use of nonlinear neural principal component analysis”. ''Journal of the Optical Society of America''. A 14 (1997): 2049–2056.〕 Also, the Abney effect does not disallow any and all straight lines on chromaticity diagrams. One may mix two monochromatic lights and not see a shift in hue, thereby suggesting a straight-line plot for the different levels of mixture would be appropriate on a chromaticity diagram.〔Fairchild, M. ''Color Appearance Models''. Wiley Interscience (2005): 117–119.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Abney effect」の詳細全文を読む スポンサード リンク
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