Illuminants

Interior color work has become much more complicated and challenging in the last 25 years with the creation of new lighting technology. Without understanding the technology and its implications, working with architectural color can feel quite chaotic. This technology has brought to our attention how different illuminants impact color differently, and what is preferred for the most natural feeling color. Different types of illuminants emit different aspects of the spectrum of light, resulting in different color temperature. Since a color’s appearance is simply light reflected, this obviously has serious implications for architectural color.

EXTERIORS

The local color is what we call a color’s appearance in natural day or white light (D65 Illuminant: “Daylight 6500 Kelvin”) at peak conditions: mid-day. As light conditions change, so does the appearance of color. While D65 Illuminant or local color is apparently the “standard” light condition under which exterior products’ colors are specified, as an architectural color consultant intentionally working at this time of day, this may be the only time we encounter D65 light conditions.

Because exterior color designs are specifying colors that will be seen in D65 Illuminant from the Sun, exterior color selection needs to occur in those light conditions. Clouds or full sunshine, the Sun’s natural intensity will provide the necessary illuminant.

On extremely sunny days, the light conditions can actually be too bright to read a color’s appearance accurately. In these situations, it is critical to find shade to also assess the colors. Regardless of the weather conditions, continually looking at the palette and design in different areas of the property, in shade and not, etc., will ensure that the most intense range of color temperature has been considered.

The best illuminant to assess exterior colors is outside from 10am-3pm, depending on the time of year and latitude of your location.

COLOR INCONSTANCY

Color (In)Constancy is the term related to a single color which changes appearance when viewed in different light sources. This is a result of metamerism: the phenomenon of how color shifts and changes in appearance. Color (In)Constancy is particularly relevant in neutral colors, which can change appearance dramatically when viewed under different light sources. An example is a khaki shade which can appear greenish in hue under D65 Artificial Daylight, but change to a brownish hue under Illuminant A Tungsten light.

INTERIORS

The Color in Space Method™ recognizes architectural color as a phenomenon of physics: it is inherently light, since we do not experience it without light. Therefore, the quality of the light impacts the perception of the color.

Color temperature is conventionally expressed in Kelvins, using the symbol K, a unit of measure for absolute color temperature. They are typically denoted by a numerical figure followed by the letter “K”. You might become a bit confused when trying to understand the Kelvin scale since it works opposite to Celsius and Fahrenheit scales. In Kelvin, lower scale values actually equate to warmer colors and vice versa.

We want the light to feel as natural as possible, for the colors to feel as natural as possible. 2550-2700 Kelvin is about the temperature/quality/warmth of natural sunlight illuminating the interior of a well-exposed home. To avoid a disparity in how your colors appear in natural daylight filtering in the windows vs. artificial light at night, use 2700 K LED lightbulbs.

The beginnings of measuring the hue of “white” can be traced back to the late 1800s and are associated with the achievements of the notable British physicist named William Kelvin, who was the first one to manage to heat a block of carbon and made notes of the changes in its color. The block of carbon naturally changed its color switching from dim red, then on to various shades of yellow and eventually reaching bright bluish white at the highest temperature. This discovery triggered the whole idea of different color temperatures of light.

Further on, as artificial lighting was introduced in our households and workspaces, and it evolved to different bulb types apart from “conventional” incandescent bulbs, such as LED and CFLs, color temperature has become considered a critical element in interior spaces. Manufacturers produce lamps and lights that have different color temperatures, and hence, now the choice is as wide as ever. But the necessary information and education about them is not getting to the average homeowner. Thus, another critical variable to manage and factor into architectural and interior color selections.