Research Of Chromatic Adaptation Transform Based On Observer Metamerism

Colorimetry is a scientific system built around color in the 20 th century.The traditional CIE colorimetry system ignores the difference of color perception between individual observers,only takes the standard colorimetric observer to represent the average visual characteristics of individuals,so as to improve the efficiency of chromaticity computations and simplify chromaticity problems.CIE1931 colorimetry system has been widely and rapidly promoted and applied in color related industry,and has made outstanding contributions to color science and color industry.But in the past few thousand years,color has jumped out of the shackles of early life as a tool to assist survival and communication,and people are more inclined to obtain the aesthetic pleasure of color from technology,design and art.In recent years,the color industry has been developing rapidly,and there are more demands for high color quality and color accuracy.At the same time,personalized,customized services are quietly rising,which is bound to become an important development trend in the future.With the changing background of the times,the theoretical development and application direction of colorimetry should also be constantly upgraded to the direction of high precision and personalization.This paper breaks through the limitation of the standard colorimetric observer in traditional chromatic adaptation models,while introducing the conception of individual colorimetric observers.Tries to conduct the chromatic adaption transform using the corresponding individual colorimetric observers.In this paper,the individual colorimetric observer model published by Yuta Asano was introduced.Based on the framework of traditional color adaptation model,the cone spectral response function of individual colorimetric observer was used to describe and transform the chromaticity in chromatic adaptation.The specific operation process of the optimized individual colorimetric chromatic adaptation model was described in detail.In order to fully characterize the distribution of corresponding color results predicted by the individual colorimetric chromatic adaptation model,a pair of combined evaluation indexes were designed,which were the mean color difference from the standard(MCDS)and the mean color difference from the mean(MCDM).On this basis,Monte Carlo algorithm is used to explore two types of individual colorimetric observers:(1)Individual colorimetric observers of specific population: It needs to in line with the specific age-population distribution structure.This paper set Chinese individual colorimetric observers as the target sample group to explore the overall law of the agespecific population;(2)Age-group individual colorimetric observers: five consecutive age groups were divided,and the number of individual colorimetric observers in each group was equal,focusing on the differences of individual chroma observers in different age groups.While introducing the concept of individual colorimetric observer into the chromatic adaptation model,the complex factors affecting the individual color vision difference are also introduced at the same time.Considering the variable factors related to the chromatic adaptation mechanism and conditions under chromatic adaptation fields,which makes the variable relationship of the individual colorimetric chromatic adaptation model more complex.Therefore,factors that affect the chromatic adaptation of individual colorimetric observers were further discussed and analyzed.From the perspective of environmental field,related variables of the field size,matching illuminants and reference color were discussed;From the perspective of model structure,the influences of different cone transformation matrixes were discussed.The results show that:(1)the chromatic adaptation results of Chinese individual colorimetric observers and CIE standard colorimetric observers are more consistent in large field of view,while there is a large difference of small field size around 3°;(2)The results of chromatic adaptation caused by different cone transformation matrices are similar,which can be ignored when discussing the difference of color adaptation results of individual colorimetric observers;(3)For chromatic adaptation results of different age-groups of individual colorimetric observers: there is an obvious dividing line of age 50,and the chroma characteristics of elderly individual colorimetric observers over 50 years old are quite different from those under 50.CIE standard colorimetric observers are more fit in with the individual colorimetric observers between 20 and 50 years old,and there is a large deviation for the chromatic adaptation results of the individual colorimetric observers who are too old;(4)For the correlation between individual chromatic adaptation results and reference chromaticity,the individual prediction results to neutral color is significantly positively correlated with brightness,and for chromatic references,their spectral characteristics should be considered comprehensively.Among different hues,individuals are most tolerant with green and yellow color,while are most sensitive to skin color and purple color;(5)For the correlation between the results of individual chromatic adaptation and visual angle: except for the elderly individuals over 60 years old,all the individuals results within else age-groups all convergent in field size of 7°.In addition,the results show that the change of visual angle only affects the green or turquoise references,while the smaller the visual angle is,the more significant the individual difference is.Individual colorimetric chromatic adaptation transform provides a more accurate way to quantify the corresponding color prediction results of individual chroma observer in chromatic adaptation.It is also a practical investigation on combining the physiological research results of color vision with chromatic model.Based on the Monte Carlo algorithm and the official data released by the Chinese population census,the color difference distribution of the chromatic adaptation results of Chinese individual colorimetric observers and CIE standard colorimetric observers under different field conditions were compared,so as to make recommendations for the field conditions applicable to CIE standard colorimetric observers here in China.According to the combination evaluation index of MCDM and MCDS,the color differences of chromatic adaptation results of standard observer and individuals under the same conditions were used to characterize the accuracy of chromatic adaptation model of standard colorimetric observer,so as to quantify the specific applicable and unsuitable situations for standard colorimetric observer,and provide guidance for the specific applicable situations of practical industrial application.