Detection of transition of red colours on Nishiki-e printings from colour-corrected digital images

Abstract

Nishiki-e (Japanese traditional polychrome woodblock print) is one of the leading products of colour culture in Japan. We tried to detect a new vivid red colour that is used on Nishiki-e printings in 1860s explosively. Red colours of 2,561 Nishiki-e printings made from 1751 to 1934 were analysed. These printings are owned by National Museum of Japanese History (Japan), and digital images have taken by a digital imaging system with a GretagMacbeth ColorChecker chart since 2003. We developed an automatic extraction software program of the ColorChecker image and a Nishiki-e image. The RGBCIEXYZ conversion matrix of each image for colour correction was calculated from the extracted colour chart image. From colour-corrected CIELAB images, strong red colours (0°≤h≤50°, C*≥20) were extracted, and frequency of use of hue and chroma was visualised as a histogram. It is clearly observed that the use of new vivid red colour (h≈10°~20°, C*≥50) was occurred in 1869. This is one of effective applications on digital archiving of coloured museum materials.