A Study on Digital Color Reproduction for Recording Color Appearance of Cultural Heritage

Abstract

The color appearance of cultural heritage are essential factors for manufacturing technique interpretation, conservation treatment usage, and condition monitoring. Therefore, this study systematically established color reproduction procedures based on the digital color management system for the portrait of Gwon Eungsu. Moreover, various application strategies for recording and conserving the cultural heritage were proposed. Overall color reproduction processes were conducted in the following order: photography condition setting, standard color measurements, digital photography, color correction, and color space creation. Therefore, compared with the color appearance, the digital image applied to a camera maker profile indicated an average color difference of Δ10.1. However, the digital reproduction result based on the color management system exhibits an average color difference of Δ1.1, which is close to the color appearance. This means that although digital photography conditions are optimized, recording the color appearance is difficult when relying on the correction algorithm developed by the camera maker. Therefore, the digital color reproduction of cultural heritage is required through color correction and color space creation based on the raw digital image, which is a crucial process for documenting the color appearance. Additionally, the recording of color appearance through digital color reproduction is important for condition evaluation, conservation treatment, and restoration of cultural heritage. Furthermore, standard data of imaging analysis are available for discoloration monitoring.

Three-dimensional deviation analysis and digital visualization of shape change before and after conservation treatment of historic kiln site

“…In particular, in the case of poorly cultural heritage sites, multiple treatments and restorations were performed in some cases [11]. Records form the crucial component of monitoring conservation conditions, and digitized records obtained using advanced equipment are gradually being increasingly used instead of the existing handwritten documents [12][13][14][15][16].…”

Extraction of Color Information and Visualization of Color Differences between Digital Images through Pixel-by-Pixel Color-Difference Mapping

“…The color difference ∆E* can easily be determined pixel by pixel. This type of detailed color difference characterization cannot be measured or visualized by conventional chroma meter measurements [1][2][3][4][5][6].…”

“…where ∆E * ab ≈ 2.3 corresponds to a JND (just noticeable difference). There are other revisions for color difference calculation formulas such as CIE94 and CIE∆E2000 [3,4,25,26].…”

“…Colorimetric measurement devices have been introduced for quantitative color analyses and data-driven objective decision-making processes in many applications including food science, biology, pharmacy, medicine, agriculture, art, and cultural heritage, to name a few. However, conventional point-of-use colorimetric devices suffer from poor spatial resolution due to the minimum sampling area requirement (greater than a few millimeters in diameter) and require direct contact with objects under illumination from an internal light source [1][2][3][4]. The colorimetric mapping of any object regardless of size and shape requires significant effort for sampling and the manual processing of the measurement data afterward.…”

“…The color differences between digital photographs and real objects cannot be easily noticed when digital photographs are taken under well-controlled lighting conditions and adhere to predetermined standards for the intensity, direction, quality, color, and spectrum of a light source. Many efforts have been made to utilize digital image files generated from digital cameras and scanners for the quantification of the color information of objects with higher spatial resolution without using conventional chroma meters [2][3][4][5][6][9][10][11].…”