虛擬照明改變下以主觀明度為錨定基準的色彩辨識

Color Identification Anchored by Brightness under Virtual Illumination Changes

為了理解不同色相的明度資訊在電腦模擬照明劇烈改變下的色彩辨識過程中是否具備貢獻，二種明度序位被視為「錨定基準」：（1）「理論明度序位」，由機器量測排序而得；（2）「主觀明度序位」，來自於受測者主觀排序而得，具有個人差異。據此，3種以明度為基準的「錨定策略」被視為研究假設，（H1）白色最亮假設（white patch hypothesis）：人們將最亮點視為純白，色彩辨識的表現最佳；（H2）灰色世界假設（gray world assumption）：人們將場景明度平均數視為錨定基準，表現最佳；（H3）黑色最暗假設（black patch hypothesis）：人們將最暗點視為純黑，表現最好。結果顯示：（1）為了使人們達成理想的色彩辨識，足夠的照明強度是必要的先決條件，但不是關鍵條件；（2）當明度序位被視為色彩辨識的錨定基準時，受測者所仰賴的明度序位，傾向於主觀明度，而不是理論明度。（3）在照明強度充足的中、長波長照明下，受測者表現雖然傾向於支持白色最亮假設，但無法以二種明度序位來解釋。據上，人們仰賴明度錨定作為色彩辨識基準時仍不具備規律性，因此不適合作為設計師用來進行色彩規劃之依據。

To determine the contribution of lightness information of different hues during the process of achieving color identification under drastic changes of illumination simulated by computer, two types of lightness ranking are considered the 'anchoring criterion': （1） 'lightness ranking' acquired through machine measurement, and （2） 'brightness ranking' acquired through the subjects' subjective ranking which is subject to individual differences. Three research hypotheses were proposed based on the above setup: （H1） white patch hypothesis （WPH） : People consider the brightest point to be pure white and this achieves the best color identification; （H2） gray world assumption （GWA）: People use the average lightness of the whole scene as the anchoring criterion and this achieves the best color identification; （H3） black patch hypothesis （BPH）: People consider the darkest point to be pure black and this achieves best color identification. The results showed that: （1） sufficient illumination is a determining factor for good color identification but is not critical; （2） when lightness ranking is treated as the anchoring criterion for color identification, the subjects tend to rely on brightness rather than lightness; （3） when there is sufficient medium and long wavelength illumination, the subjects' performance tends to support the WPH but this can't be explained with either type of lightness ranking. This study therefore concludes that lightness ranking does not suit to be the criterion of color planning to designers, because the lightness ranking still does not possess regularity in color identification yet.