Research On Light Sources For Chinese Traditional Painting Based On The Least Damage To Painting Colors

Chinese traditional paintings are one of the important elements of the world's cultural heritage,most museums hold a large number of precious Chinese paintings.According to the CIE,the standard of museum illumination design is “highly responsive” in terms of chemical stability.Optical radiation from any light source causes permanent damage to Chinese traditional paintings.Chinese traditional painting has the characteristics of abundant stock,high-value and vulnerability,and is an important type in the research of exhibition illumination.At present,the research for illumination protection on paintings mainly focuses on Western paintings,such as oil paintings;and very few studies focus on Chinese traditional paintings.At the same time,the current researches are mostly about traditional light sources such as metal halide lamp and halogen tungsten lamp.The WLED is currently a hot topic in the field of exhibition illumination due to its advantages,the luminous principle and spectral irradiance distribution of WLED is different from the traditional light source.The practical of RYGB-type WLED applicability lacks scientific basis and the damage degree to painting are unknown up to now.In addition,WLED has a special light emitting principle,the spectral power distribution(SPD)of its output spectrum can be adjusted as necessary in order to create the least-damaging WLED possible.A solution to the above problems is derived by constructing the experiment in optical laboratory.The experiment utilized a WLED as experimental light source,and a tungsten halogen lamp,a metal halide lamp as contrast light sources.The painting specimens were crafted by the Chinese Traditional Painting Institute of Tianjin University.The chromaticity coordinate was measured at the end of each illumination cycle: First,the dominant wavelength,excitation purity,and lightness were calculated based on the data,by analyzing the curves showing the chromaticity change of different pigments under different light sources to determine the color change rules;and second,by calculating the color change values to determine the influence of light sources on the painting.Moreover,four typical monochromatic light sources(red,yellow,green,and blue),comprising of WLED spectrum,were used to illuminate the painting specimens.The chromaticity coordinate was measured at the end of each illumination cycle,the same method was used to determine the influence rules of the main monochromatic lights on painting.And the spectrum constitution suitable for different painting types could be appropriately defined,then it would be meaningful to develop the least-damaging WLED-series light sources.The illumination damage from RYGB-type WLED is less than metal halide lamp and halogen tungsten lamp.The light sources had the most pronounced effect on the lightness of inorganic pigment,followed by the effect on the excitation purity,whereas the hue was the least affected,proving that the lightness is the main factor that influences the change of Chinese traditional heavy color paintings.In order to most effectively protect these paintings from illumination damage when utilizing WLEDs,the monochromatic light proportion of the WLED should be tailored to each specific type of painting.These results provide a data base for the related research and also provide a reference for choosing light sources in the design of museum lighting.The conclusions can guide the museum staffs to better protect the cultural relics and reduce the damage caused by artificial lighting.