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SPIE Professional April 2008

True Colors

Wendy Davis, a NIST scientist and SPIE member, is working on standards for color quality in solid-state lighting and other illumination sources.

photo of Wendy Davis
In a corner of Wendy Davis’ lab at NIST headquarters in Maryland, two light boxes illuminate a variety of ordinary objects. One box is lit by one type of light bulb, the other lit by another type. The same set of objects is in each box, but the two lights render their colors remarkably—and almost eerily—different.

The setup isn’t just a fun experiment. Davis and her colleagues are addressing problems with the Color Rendering Index, which is maintained by the Commission Internationale de l’Eclairage (CIE or International Commission on Illumination), for solid-state light sources.

Working closely with the lighting industry, Davis and her group, led by physicist Yoshi Ohno, are developing a Color Quality Scale to better assess the color rendering properties of illumination sources such as solid-state lighting. The scale evaluates several aspects of the quality of the color of objects illuminated by a light source, accounting for color rendering, humans’ ability to distinguish between colors, and observer preferences.

This work at NIST’s Optical Technology Division is helping to meet the needs of the lighting industry and its consumers, leading to better ways of communicating the color quality of lighting. When the scale is completed, Davis and her group plan to propose it as a new international standard.

The group is also working to develop a standard for the effective intensity of flashing lights, another industry need. And this past year, they performed a pilot study to compare measured colors with perceived colors for roadway signs. Based on the results, a larger study is under development at Federal Highway Administration laboratories.

Davis, an SPIE member, earned her PhD in vision science in 2004 at the University of California at Berkeley and later accepted a National Research Council postdoctoral fellowship at NIST. Afterward, she became a full-time NIST staff scientist. She performs a wide variety of tasks, from preparing color samples to taking measurements. She also serves as chair of the CIE’s “Colour Rendition by White Light Sources” committee. She is active at conferences, including SPIE meetings.

When asked about a typical day in her lab at NIST, she replied, “Luckily for me, there is really no such a thing as a ‘typical day.’”

Whether as staff or guest researcher, working at NIST is rarely a routine experience.

DOI: 10.1117/2.4200804.04

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