In November 2006, the Yamaguchi Prefectural Art Museum in southern Japan held an exhibition entitled 'The Trip to Sesshu'. It commemorated the 500th anniversary of the death of the Zen Buddhist monk and painter Sesshu Toyo, whose delicate suibokuga ink paintings have been designated 'National Treasures' by the Japanese government.
So that visitors could appreciate Sesshu's scrolls as closely as possible to the way original admirers did — under candlelight or torchlight — some of the paintings were illuminated by a specially designed light-emitting diode (LED) system. Tsunemasa Taguchi and Michitaka Kono now provide the technical details of that system (T. Taguchi and M. Kono J. Light Visual Environ. 31, 149–151; 2007).
LEDs are solid-state light emitters known for their energy efficiency, flexibility of design and robustness. For a long time, they were made to emit light only in a particular part of the visible-wavelength spectrum. But in the mid-1990s a new generation emerged, based on blue LEDs covered with a yellow phosphorescent layer, which emitted bright, white light.
Taguchi and Kono's lighting system used special LEDs that contained three different phosphors, each emitting at different frequencies. This meant that the white light emitted had a particularly high colour quality, as quantified on a scale known as the colour-rendering index. To optimize viewers' appreciation, the authors tailored the LEDs to render the earthy red colours characteristic of the antique scrolls especially well.
The individual lights were positioned so as to distribute light evenly on the artwork (first two paintings pictured), rather than scattering it around them as fluorescent lamps would do (paintings in background). The output of the LEDs was stable and did not cause heating, thus assisting preservation of the precious scripts.
White LEDs are becoming ever brighter, more efficient and less expensive. As a result, traditional light bulbs are increasingly on the way out. Large-scale applications, such as car lights, traffic signals and Christmas decorations, are where the economic benefits of LED use are being felt. But the illumination of antique Japanese art must surely rank as one of the diodes' most aesthetically pleasing applications.
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Venema, L. The art of illumination. Nature 450, 1175 (2007). https://doi.org/10.1038/4501175a