PNNL

The room has faux walls, a table with place settings, fresh fruit, boxed cereal, snack items, overhead light, and some clothes. It’s a room-within-a-room, designed specifically for testing color rendition—that is, how the color of objects around you change when doused with various light sources.

Michael Royer and his team designed the room, located in the Lighting Science and Technology Lab (Portland, OR) in 2015 for a series of studies aimed at updating guidelines for color rendition. The Illuminating Engineering Society and American National Standards Institute recently adopted new metrics, resulting from these studies, that replace standards that have been used for decades.

“The past color rendition standards were often considered ‘acceptable’ but with recognized flaws,” said Royer. “They didn’t take into account new lighting technologies developed over the past few decades. Given PNNL’s expertise in energy efficiency and lighting research, it made sense for us to help develop the new standards.”

But first, they needed a secret lighting lair.

“We needed a space where we could control the lighting conditions and have objects in it that one might find in a typical household,” said Michael Royer. “In each of the three studies, we invited more than 25 individuals to sit in the room and answer a series of questions as we manipulated the light. We asked if they considered it natural, shifted, dull, or saturated. And then we asked whether or not they liked it and if it was at least ‘acceptable’.”

The Tradeoffs

Why so much subjectivity?

There’s a trade-off between energy efficiency and color. “The most efficient color of light for achromatic visual tasks such as reading text is green. But it’s hardly pleasing to most people,” explained Royer.

Advancements like compact fluorescent lamps and light-emitting diodes have changed consumers’ experience with lighting. Whereas there was once a simple choice of how much light (wattage) a consumer desired when purchasing incandescent lamps, there’s now a variety of choices to be made about the appearance of the light and its effect on a room. This increased variation requires better metrics, and associated performance guidelines, so that the effects can be recorded without requiring hands-on tests of every product.

The third and final study in 2018 validated the team’s earlier findings on color rendition and informed the IES/ANSI’s latest appendices to TM-30-18, the standard for evaluating light source color rendition.

“It’s a fun and interesting project,” commented Royer. “Lighting is part of our everyday lives. Manufacturers and those in lighting design, for example, will hopefully find a lot of value in the new standards.”