Penn State research on color rendering reinforces Soraa's LED claims

Sept. 23, 2014
Test subjects in a color-rendering research project preferred the performance of Soraa's LED source that is based on a violet-pump LED combined with a combination of three phosphors designed to deliver a broader spectrum.

Test subjects in a color-rendering research project preferred the performance of Soraa's LED source that is based on a violet-pump LED combined with a combination of three phosphors designed to deliver a broader spectrum.

Soraa has announced the results of a joint research project with Pennsylvania State University (Penn St) that evaluated human color-rendering preference for solid-state lighting (SSL) sources. Test subjects widely preferred the performance of Soraa LEDs illuminating color and white objects relative to the performance of an 85-CRI source that also delivers a relatively broad spectrum.

The results of the research have been published on the Lighting Research & Technology academic website. The study gathered the preference of test subjects that viewed color and white objects under a Soraa LED source compared to a more typical LED based on a blue pump. The Soraa LED uses a violet pump and three phosphors, whereas more broadly deployed LEDs use a blue source and a two-phosphor mix. Soraa has consistently claimed an advantage in color- and white-point performance for its technology.

The study compared the perception of colored objects, a white shirt, human skin, and teeth under the two sources. The 48 participants largely preferred the Soraa light sources across the series of experiments.

Soraa is touting the results to make the point that light quality should be considered as important as efficacy in the choice of light sources. "There are those who’ve asked: does color and whiteness rendering really matter? Well, it does, and we now have the data to prove it," said Mike Krames, CTO of Soraa. "Because all of our lamps render the entire visible spectrum, white fabrics and paper goods pop, plastics are brilliant, and people’s smiles are whiter, and colors are more natural and beautiful. That’s good news for consumers and retailers, who want and deserve the enormous economic and environmental benefits of LED lighting, but are unwilling to sacrifice the sales benefits of excellent light quality in return."

The Penn St research, however, leaves more questions unanswered than it actually answers. There is the question of what premium people will pay for higher quality. Moreover, most anyone would expect a 97-CRI Soraa light source to outperform an 85-CRI source in terms of color or white preference.

What is without question is that there are developments that go beyond characterization by the CRI metric that can influence consumer preference. Soraa was the first LED maker to promote the benefits of a violet emitter and the three-phosphor mix, especially in terms of white performance including those that use optical brightening agents. Now other vendors such as Philips Lumileds and Luminus Devices are experimenting with new LED formulations for better white rendering. And LED module manufacturer Xicato has developed products that eschew high CRI for color rendering of saturated colors that CRI penalizes.

Indeed, the most important takeaway from the Penn St research is neatly summarized in a blog post by Krames, who worked with the Penn St researchers on the study. Krames addressed a recent IES (Illumination Engineering Society) position paper on how color requirements should be used in energy-regulatory programs. Soraa has long been opposed to efficacy requirements that aren’t set in consideration of the color performance of an LED lighting product.

In the blog post, Krames reopens the argument that CRI is simply an insufficient metric for defining color or white performance, and that the industry needs a new metric. Moreover, he makes the case that the industry needs a dedicated metric to measure the accurate illumination of white objects. We agree on both counts.

Meanwhile, we also look forward to research that compares the Soraa technology and other approaches to optimum color and white-point rendering. Indeed, a study that compared Soraa lamps with the Lumileds CrispWhite technology and Xicato Vibrant, among others, could prove very interesting.

About the Author

Maury Wright | Editor in Chief

Maury Wright is an electronics engineer turned technology journalist, who has focused specifically on the LED & Lighting industry for the past decade. Wright first wrote for LEDs Magazine as a contractor in 2010, and took over as Editor-in-Chief in 2012. He has broad experience in technology areas ranging from microprocessors to digital media to wireless networks that he gained over 30 years in the trade press. Wright has experience running global editorial operations, such as during his tenure as worldwide editorial director of EDN Magazine, and has been instrumental in launching publication websites going back to the earliest days of the Internet. Wright has won numerous industry awards, including multiple ASBPE national awards for B2B journalism excellence, and has received finalist recognition for LEDs Magazine in the FOLIO Eddie Awards. He received a BS in electrical engineering from Auburn University.