摘要
为提高彩色印刷品的颜色质量评价精度,围绕CIE推荐的9个颜色中心,制作了450对颜色样本,组织了26名专业组和17名非专业组共43名观察者开展色差评价实验。实验结果表明,专业组的观察者精度较非专业组高,且颜色分辨敏感度高。以标准化残差平方和为优化指标,对CIELAB和CIEDE2000色差公式分别进行明度差因子(k_(L))、饱和度差因子(k_(C))和色调差因子(k_(H))的加权优化以及幂指数优化。计算结果表明,观察者对色调差的变化最为敏感,需要在现有色差公式中增加色调差的权重。进一步地,给出了针对不同专业背景观察者的印刷品可接受色差阈值和色调差阈值,以提高产品的颜色质量检测准确性。
Objective Color difference is a crucial index used by the industry to evaluate the accuracy of color reproduction,especially in fields like display,textiles,and printing.However,in practical application,there are instances where the color difference measured by instruments exceeds tolerance limits but is visually acceptable,or where the measured color difference is within tolerance but is still visually unacceptable.This inconsistency may arise from the various components of total color difference,including lightness,hue,and chroma differences,which evoke varying color perceptions in the human eye.The challenge is to align the calculated color difference with the visual color difference perceived by humans,which remains a key technical issue.Methods To improve the accuracy of color quality evaluation for printed samples,two experimental groups are conducted simultaneously:one at the Beijing Institute of Graphic Communication(Exp.I)and another at Suining Kuanzhai Printing Company(Exp.II).In each experiment,450 pairs of printed samples,representing the nine CIE-recommended color centers,are prepared,with CIELAB color differences ranging from 0.27 to 3.88(mean is 1.91 in Exp.I)and from0.21 to 3.92(mean is 2.04 in Exp.II).Lightness difference(ΔL~*),hue difference(ΔH~*_(ab)),and chroma difference(ΔC~*_(ab))contribute differently to the total color difference.A total of 43 observers(17 inexperienced observers in Exp.I and 26experienced observers in Exp.II)participate in the color difference experiments.These experiments are conducted indoors with natural light from a north window,during fixed time intervals(9:00—11:00,14:00—16:00)on a sunny day to ensure stable viewing conditions.In total,22950 observations are collected in each experiment.The probabilities(P)for an“unacceptable color difference”are then converted into a standard normal distribution Z-score to obtain the visual color difference(ΔV).The standardized residual sum of squares(STRESS)index,recommended by CIE,is used to assess the performances of the calculated CIELAB and CIEDE2000 color differences compared to the visual color differences.Results and Discussions The wrong decision(W_D)results show that experienced observers outperform the inexperienced group,exhibiting higher sensitivity to color differences.Moreover,optimization of the k_L∶k_C∶k_(H)factors for lightness difference,chroma difference,and hue difference is applied to the original CIELAB and CIEDE2000 color difference formulas.In addition,a power function approach is used to minimize the STRESS value in both formulas.The results indicate that observers are more sensitive to hue differences,and therefore,it is essential to increase the weight of hue differences in the existing color difference formulas.To provide a practical method for enterprises to efficiently evaluate the color quality of printed samples,the consistency between the calculated results(e.g.,ΔE andΔH values),and visual color differences is examined.It is found thatΔE values optimized by k_(H)factors in CIELAB,andΔE values optimized by k_(L)factors in CIEDE2000,along withΔH thresholds,can improve consistency compared to other optimization methods.Conclusions Color quality control and evaluation are critical in the process of reproducing printed samples.In the CIEL~*a~*b~*color space,hue difference is more closely aligned with visual color difference than lightness and chroma differences.Based on this,we propose corresponding color difference and hue difference thresholds to improve the accuracy of product color quality evaluation for observers with different professional backgrounds.Specifically,the recommendedΔE_(T)values in CIELAB and CIEDE2000 are 1.47 and 1.20,while the recommendedΔH~*_(ab,T)andΔH_(00,T)values are 0.65 and 0.45 for inexperienced observers.For experienced observers,the recommendedΔE_(T)values in CIELAB and CIEDE2000 are 1.02 and 0.86,and the recommendedΔH~*_(ab,T)andΔH_(00,T)values are 0.53 and 0.34,respectively,for quality inspection processes.The methods and results presented in this study can also be extended to other fields such as lighting,display,textiles,and printing.They offer valuable guidance for color quality evaluation.
作者
尚晓宇
黄敏
公绪平
王丹
李修
刘瑜
Shang Xiaoyu;Huang Min;Gong Xuping;Wang Dan;Li Xiu;Liu Yu(School of Printing and Packaging Engineering,Beijing Institute of Graphic Communication,Beijing 102600,China)
出处
《光学学报》
北大核心
2025年第1期310-319,共10页
Acta Optica Sinica
基金
北京印刷学院科研创新团队项目(BIGCEc202302)
北京印刷学院青年托举项目(Eb202402)。
关键词
视觉光学
视觉色彩
色差公式优化
可接受色差阈值
可接受色调差阈值
visual optics
visual color
color difference formula optimization
acceptable color difference threshold
acceptable huedifference threshold
