Okayama Castle

The silhouette and atmosphere of the Tenshu (tower keep) of Okayama Castle are said to change depending on the viewing angle. In illuminating the Tenshu, we conducted lighting simulations using Environmental Planning Support VR and simulation software in the preliminary stages, considering how the structure’s appearance changed depending on the positioning of lighting. Next, in considering which colors to use in the illumination, we used an original program to finely adjust colors in order to accentuate the black and white of Okayama Castle and make the contrast of dark and light appear even more beautiful.

Previously it was difficult to perform pre-illumination assessments of the castle architecture in advance, but with the use of simulation software, it is now possible to conduct realistic lighting evaluations beforehand. Optimal illumination was achieved by using 3D simulations to assess the three-dimensional façade and analyzing how to achieve uniformity of brightness through color illuminance distribution.

Using simulation software made it possible to assess the illumination for individual fixtures, enabling optimal lighting fixtures and shooting angles to be evaluated.

Previously, it was necessary to employ electrical technicians to actually install the lighting fixture in order to adjust angles, a process that took considerable time. By using simulation software, we were able to verify illumination points in advance, enabling smooth adjustment of angles.

Adjusting angles while checking illumination points

We designed illumination using awareness colors that would combine the creation of a vibrant spectacle in conjunction with raising awareness at night year-round. Through meticulous measurements and adjustments, we were able to express colors that exude a sense of comfort when people gather together while at the same time enhancing color reproducibility.

In recent years, a movement known as “Awareness Color Illumination,” in which lighting displays use theme colors indicating support for certain awareness-raising campaigns, has been gaining traction. Awareness color illumination makes it possible to subtly convey messages of social awareness in addition to making the nighttime view of the castle more enjoyable for visitors. At Panasonic, through subjective evaluation experiments and field surveys that we conducted in locations around Japan, we measured the colors used in awareness lighting events, enabling us to verify what colors people find pleasant. Based on these findings, the color illumination of Okayama Castle uses colors that people find appealing.

Subjective evaluation to identify pleasant colors

Because the lighting colors change depending on the color of the illuminated surface (castle), quantitative evaluations were carried out using a spectral radiance meter while varying the colors. After installation of the lights, Okayama Castle was illuminated based on the preferred chromaticity value and fine adjustments were made incorporating visitors’ feedback.

Color adjusted to the preferred chromaticity value for blue (u’: 0.18, v’: 0.17) using measuring fixture

Designated as a national important cultural property, the Tsukimi-yagura turret is the only turret within the ruins of Okayama Castle’s Honmaru (main enclosure and keep) still in existence. Because the Tsukimi-yagura turret and Okayama Castle were illuminated with different floodlights, the chromaticity of the light differed. (Tsukimi-yagura turret: LED floodlights, Okayama Castle colored lighting fixtures).
Accordingly, illumination for Okayama Castle was finely adjusted using an illumination controller so that the chromaticity of the castle and Tsukimi-yagura turret matched, achieving illumination with uniform chromaticity for the two buildings.