Specifying color quality appropriate for the application is essential. In a high-end retail application, good color quality can make products, especially clothing, appear more vibrant, truer and ultimately more appealing. In an office application, color quality can facilitate social interaction by rendering faces more naturally and thereby helping to create a more productive and appealing work environment. In a hospital application, good color choices can make guests feel more welcome by imitating the warm lighting conditions of home. The list goes on.
Think about the application: Do you want it to be visually warm or visually cool? The right color temperature is often a matter of psychology—both preference and tradition—with due consideration for emphasizing (and not distorting) dominant colors in the space and properly rendering color contrasts that make tasks more visible or call out safety markings and instructions. In cooler northern climates, people tend to prefer warmer light sources, while in warmer southern climates, people tend to prefer cooler light sources. Note that people need to look as good as objects, spaces and furnishings in the space; one study indicates that people (regardless of race) have a preference for neutral color temperatures (3000K-4100K) as rendering skin tones most pleasantly (Quellman and Boyce, 2002). At home, people tend to prefer warmer light sources, while at the office, cool or neutral light sources are preferred. Research also suggests that people are more accepting of warm color temperatures at lower light levels and cool color temperatures at higher light levels. “This makes sense when one remembers that traditional sources of low-level illumination for people were open fires, torches, candles and oil and gas lanterns—all sources rich in the red region of the spectrum,” Gary Gordon notes in an article published in Architectural Lighting Magazine. “Traditional sources of high-intensity illumination have been the sun and sky, both relatively ‘cool’ colors of ‘white’ light.”
In many applications, the higher the CRI the better, with 80-100 being optimal for rendering colors more “naturally”—that is, how most people would expect them to appear, and >90 for color-important applications, such as retail applications where merchandise appearance and appraisal is critical. Many energy-efficient light sources, from T8 linear fluorescent to ceramic metal halide, offer good color quality.
Fruit viewed under a warm light source (left), a neutral source (middle) and a cool source (right). Photo courtesy of OSRAM SYLVANIA, Inc.
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