不同光泽度色样仪器测量色度变化的研究

Chromaticity Changes of Instrument Measurement for Color Patches with Different Gloss Levels

研究了两种仪器测量色度随色样光泽度变化的规律。基于Dalal-Natale-Hoffman1999反射模型,预测三种几何测量条件下5种光泽度的35个色样三刺激值。采用非线性指数函数建立三种几何测量条件下黄色样和蓝色样光泽度-预测值明度、彩度和色调模型。结果表明,包含镜面反射(di∶8°)测量预测,随着光泽度增加,明度、彩度和色调保持恒定;排除镜面反射(de∶8°)和45°环形照明0°方向接收(45°a∶0°)测量预测,随着光泽度增加,色调保持恒定,明度减小和彩度增加。将仪器测量值明度、彩度和色调对预测模型进行验证。结果表明,黄色样的光泽度-明度、彩度和色调预测模型对其他光泽度下明度、彩度和色调的预测是可行的,蓝色样的光泽度-明度和彩度预测模型有待改进。

Chromaticity changes of two instrument measurement for color patches with different gloss levels are investigated. The tristimulus values are predicted based on Dalal-Natale-Hoffman1999 reflection model for thirty- five color patches printed in five kinds of paper with different gloss levels for three geometrical measurement. For yellow samples and blue samples, a nonlinear fitting algorithm by exponential function is applied to develop the model between gloss and predicted lightness, chroma and hue among three geometrical measurement. The results show that for specular light included （di： 8°） geometries, predicted lightness, predicted chroma and predicted hue are constant. For specular light excluded （de： 8°） and 45°a： 0° geometries, predicted lightness decreased with increasing gloss for all color patches, predicted chroma correspondingly increased and predicted hue was constant. Meanwhile, measured lightness, chroma and hue are used to characterize accuracy of predicting model. The results also illustrate that for yellow samples it is available to predict chromaticity changes of instrument measurement for a wide range of gloss values for the model between gloss and predicted lightness, chroma and hue. However, for blue samples it is unavailable and need to improve.