用于计算机配色的反射光谱数据质量评估方法研究

摘要

Spectral reflectance data quality is important for computer color matching.There are two existing methods for evaluating the quality—spectral reflectance method and K/S method,which are too complex to apply.In this paper,45°/0°and d/8°geometric conditions are used in the measurement of spectral reflectance of the offset ink samples printed on coated paper and silver-foiled paper while improvement on the geometric condition is made on the basis of the spectral reflectance method.Moreover,a new evaluation method—light-ness and chromaticity comparative method is put forward,and comparison is made among the three methods. The results show that both 45°/0°and d/8°are feasible in the measurement of spectral reflectance of coated pa-per;however the former one cannot meet the requirement of spectral reflectance measurement of silver-foiled paper.In addition,as to d/8°Specular Component Included (SCI),when the silver-foiled paper is taken as the substrate,the reflectance of transparent white ink samples are smaller than that of other primary inks;and ab-normal intersections appear in the curves of cyan and magenta ink respectively at the concentration of 60%,re-sulting in a poor spectra quality at high ink concentration;In the figure of lightness and chromaticity curves, there is significant divergence of the cyan and magenta ink curves from the referenced coated paper.In conclu-sion,the spectral reflectance of the transparent ink should be greater than or at least equal to other primary inks,and the maximum concentration of cyan and magenta should be limited;when the coated paper with good diffusion performance is taken as the reference,the comparative analysis is more intuitive than the two existing methods.%基础色样的反射光谱数据质量是影响计算机配色结果的重要因素之一。目前评价配色反射光谱数据质量的方法有反射光谱检测法和K/S检测法,但这两种方法需检测每种基础色样和各个波长的反射率与K/S值,检测过程过于复杂,故不适用于光谱数据质量的快速直观检测。本文使用45°/0°和d/8°几何条件的分光光度计测量以铜版纸和银卡纸为基材的胶印油墨基础色样反射光谱数据,基于光谱检测法优化获取基础色样反射光谱数据的几何条件,提出了一种明度色度对比检测法；并对比分析了反射光谱检测法,K/S检测法和明度色度对比检测法。结果表明,45°/0°和 d/8°几何条件均可用于铜版纸基础色样反射光谱数据的测量,但45°/0°几何条件不符合银卡纸基础色样反射光谱数据的测量要求；而对于d/8°分光光度计,在包含镜面反射时,银卡纸为基材的透明白反射率小于各基色墨反射率,且青墨与品红墨反射率分别在浓度为60%开始出现异常交叉,从而导致高浓度区域光谱质量较差；而在明度色度对比检测图中,青墨与品红墨样条与参考铜版纸基础数据偏离更加明显。故须选择大于或等于各基色墨反射率的透明白,基础色样中需约束青墨与品红墨的最大浓度；以漫反射特性较好的铜版纸作为配色基材时,明度色度对比检测法检测效果较现有两种检测法更为直观。