Requirements Analysis for Print Reproduction of Gold Leaf
Appearance

Takayuki HASEGAWA**, Koichi IINO**, Toshiya NAKAGUCHI*** and Norimichi TSUMURA***
***Chiba University, JAPAN
**Toppan Technical Research Institute, Toppan Printing Co., Ltd.

To appear in JPST Vol.48, No.6,pp. 417-415 (2011)

A fundamental study was conducted to analyze the requirements for appropriately reproducing the appearance of gold leaf on print without metallic inks in cases where accurate colorimetric matching is not possible because of the large difference in the luminance range. Based on the pixel-wise bidirectional reflectance distribution functions（ BRDFs） and surface normals of a gold leaf sample（ a sheet of gold leaf pasted on a sheet of Japanese paper）， a wide variety of print reproductions under different geometric conditions of image rendering and luminance compression were created using computer graphics. A visual experiment was carried out where the observers evaluated the reproducibility of the appearance of the original gold leaf sample on the prints. The results of this visual experiment show that the requirements possibly include the following:（ 1） spatial change in brightness（ or lightness） in the gold leaf region should be apparent through control over geometric conditions for image rendering,（ 2） the brightest area in the gold leaf may not necessarily be as bright as the print gamut, and （3） the darkest area in the gold leaf should be sufficiently dark when compared with the brightest area.

[PDF] (reprint)[in japanese]