蛍光画像
目で感じることのできる光(可視光)の中でも比較的波長の短い特定の波長を画面に照射し、画面上にある物質自体が発する蛍光反応を撮影します。これにより、例えば表面上は似た色合いでも異なる画材が用いられた箇所や、制作当初に用いられたのとは異なる画材による補筆箇所などがわかります。
この蛍光画像では、向かって左側の橋桁の部分や橋を架けた老翁と見られる人物の白い衣は強い蛍光反応を示しており、橋の敷板部分や基礎工事をしている場面の橋脚とは異なる絵具が用いられていることがわかります。またどこにどのように補絹(画絹の欠損部分を修復の際に補塡したもの)が存在しているか明確に識別できます。

Fluorescence Image
Light of a specific wavelength—relatively short within the range of visible light perceptible to the human eye—is projected onto the surface of the painting, thereby recording the fluorescence emitted by the materials on the surface. This method makes it possible to identify, for example, areas where different coloring materials were used even though they appear similar in color on the surface, as well as areas that were later retouched with materials different from those originally used.
In this fluorescence image, the bridge girder on the left side of the composition and the white robe of the figure believed to be the old man who constructed the bridge exhibit a strong fluorescent response, indicating that pigments were employed that differed from those used in the planking of the bridge and the bridge piers in the scene of the foundation work. In addition, the locations and extent of infill silk inserted during restoration can be clearly identified.