The World of Illusion vs Allusion: Reality vs Expectation in Cultural Context of Lighting Design (Essay Series 4.1)
“The appropriate choice of direction for a project is then a mirror to the cultural and historical context, through the prism of illusion or allusion.”
Lighting of Historic Buildings
While exploring and analyzing design solutions for the lighting of historic buildings, there is often an important distinction that needs to be made pre-facto. Shall we pursue options that allude to the architecture, or willfully create illusions that are superimposed on a willing architecture? Through this analysis arises two distinct visual worlds — a world of illusion or a world of allusion. The appropriate choice of direction for the project is then a mirror to the cultural and historical context, through the prism of illusion or allusion.
Even though electric lighting can never have the same characteristics as daylight, some buildings require that their color appearance be preserved at night and enhanced, if possible, by lighting them toward a higher chroma (in the world of allusion). By contrast, some projects willfully ignore the requirement of the electric lighting to render the building to its appropriate color and use the building as a canvas to paint new colors, using overt pigmentation to create illusions. There is no right or wrong approach here, but two different sides to the coin. However, if we are seeking a sensitive response to the architectural details and heritage, we tend to lean toward the world of allusion.
Historic buildings, especially those preserved by local regulations and interests, have an architectural character that reminds the local community of their heritage and is an important cultural connection to the past. In most historic buildings, a combination of material types is used, with a contrasting stone used as a trim or for relief work. The materials on such buildings have different types of texture and can range from being very smooth to highly rough.
In our professional work, AWA has explored the relationship between the spectral power distributions of light sources, various building materials, and human judgments of preference.
Because most lamps used currently (LEDs) have discontinuous spectral power distribution (SPD)characteristics, their use can cause unexpected shifts in the color appearance of building materials relative to their appearance in daylight conditions. These shifts can lead to negative subjective reactions from those viewing the building.
We have studied the effects of electric light sources on the colors of materials and have shown that the “preferred” color of an object under an electric light source is more saturated than its color appearance under daylight (Wadhwa, Davis, 1996). For building facades, this preference for higher color saturation may also be linked to the concept of “memory colors.”
Having seen a building under daylight, the viewer relies on his or her memory to recall the color appearance of the building materials. Memory colors tend to be characteristic of the dominant chromatic attribute of the object in question and more saturated than the actual color of the object. Because of this, a viewer expects to see the building materials as more saturated under an electric light source at night than it appeared when viewed in daylight conditions. If the chromaticity of the material at night under electric light matches the chromaticity of the material under daylight, the viewer’s response is expected to be less than favorable because they’ve compared the nighttime appearance of the material with their memory of the daytime appearance, and, thus, expect to see a more saturated material. Therefore, a lamp that shifts the coordinates of the material toward greater saturation along its dominant wavelength would be preferred as it would more likely meet the expectation of the viewer. Two experiments were designed and undertaken to test this hypothesis. The purpose of the first experiment was to validate that memory colors shift toward greater saturation. The second experiment was conducted to examine the subjective preference for stone under different light sources, which changed the chroma of the stone (hue and value kept constant). Three types of colored stones, typically used on historical facades, were used for the experiment. The data analysis indicates that a significant difference does exist and the results are consistent with what was expected. Based on this, it is preferred that the lamp used for lighting historical facades saturates the chroma of the material in the direction of its dominant wavelength. It is important to note that the range of saturation for memory colors is localized around the actual chroma and does not extend to the spectrum locus.
This study was a step toward answering the question of color preference and saturation in lighting of colored building materials using electric light. However, issues connected with the outer two dimensions of color — hue, and value — are being studied further for their interaction with memory and subjective preference. Physical properties of building materials, such as texture, architectural styles, and a combination of stone types are also being studied for their effect on color preference.
The appropriate choice of direction for a project is then a mirror to the cultural and historical context, through the prism of illusion or allusion.