Craig Bernecker, Ph.D., director, Lighting Education Institute and professor at Parsons The New School for Design, recently gave a talk as part of the ongoing Philips Lighting University series of webinars. The webinar, “Lighting and Well Being: Illustrations of Psychological and Physiological Effects,” is available for free viewing at lighting.philips.com.
In his speech, Bernecker describes the influence of lighting on human performance, environmental preference, perception, impressions and behavior in work environments. It’s understood that light produces physiological effects, and people need a minimum light level to perform a task efficiently, accurately and safely. More interesting to lighting practitioners now, research supports decision-making in what might be called the art of lighting—where to position light in a workspace and at what relative intensities to influence perception.
Research studies indicate that light should be placed where people are going to look, with focus on the brightest part of the field of view. Research by John Flynn at Kent State University/General Electric Lighting Institute (1971–1975) found that people, when relaxing, tend to prefer a relatively dim part of a space oriented toward the brightest area, but they prefer a relatively bright part of the space while working.
This tendency can influence behavior. Research by Eugene W. Sucov and Lyle H. Taylor in the 1970s showed that, when subjects were told to enter a room by going around a barrier to get to a task on the other side, they tended to go right. When brightness was increased on the left compared to the right, more people tended to go left. The more brightness increased, the more people went left.
Increasing relative brightness is the key to creating focal points in a space. In a retail store, it can attract shopper attention to key merchandise. In public spaces, it can support wayfinding. In an office, however, an emphasis on strong contrasts can be visually fatiguing and distracting. In these work environments, people tend to prefer high levels of uniform brightness.
To support this theory, Bernecker cited various studies that suggest most people prefer a higher light level than is necessary for good performance. This is not positive news from an energy point of view, but it’s important to recognize because preference is related to satisfaction. The solution may not be to raise light levels with its associated energy cost but to influence perception of light levels based on brightness contrast. Higher contrast correlates to perception of a higher light level. The challenge is that too much light can be tiring to the eye (or, in extreme cases, glaring). What’s more, research suggests people tend to prefer more uniform brightness than is necessary to avoid visual fatigue.
The solution may be to increase peripheral brightness in a space through high-reflectance walls, wall lighting or both. In other research conducted by Flynn, study participants were exposed to a room illuminated four different ways and asked to rate it on a seven-step semantic differential rating scale between opposite impressions, such as pleasant/unpleasant, bright/dim, spacious/confined, public/private and so on. The four lighting approaches, or modes, included overhead/peripheral (lighting in center of room versus the walls), uniform/nonuniform (uniform distribution versus spots/pools of higher intensity), bright/dim (more light versus less light on workplane), and visually warm/visually cool. Flynn’s studies suggest that bright, uniform lighting, with some emphasis on walls, can influence impressions of visual clarity.
One way to achieve this is through indirect lighting, which promotes uniformity while increasing brightness on walls. The lighting industry responded to this in the late 1970s/early 1980s by introducing wholly indirect (100 percent uplight) luminaires. But another problem emerged; people found the spaces dimmer instead of brighter.
The solution was to add a downlight component. Researchers at Penn State found that people consider a space as having a higher light level if they have a sense of the light source, thinking that ultimately led the lighting industry to shift from wholly indirect luminaires, which emphasize the ceiling plane, to products that emit some downlight. Another study (K.W. Houser, et al., 2002) followed this study by finding that people in a typical work environment tend to prefer luminaire distribution that is neither wholly direct nor indirect but something in between. The majority of participants in that study preferred direct/indirect (40–60 percent uplight) or semi- indirect (60–90 percent uplight) luminaire distributions.
So many elements influence human behavior that it’s difficult to isolate lighting as a sole deciding factor. However, research suggests lighting method can influence perception, and this supports current thinking that placing light on walls through direct/indirect or semi-indirect luminaires can cultivate perception of higher light levels.