Right after receiving my PhD, I took a position as a research scientist at the National Research Council Canada (NRCC) in Ottawa. It was a very good decision. The NRCC was populated and managed by scientists and engineers who understood their collective role as providing a solid foundation for decision-making by Canadian industry and politicians.

By Colleen Hufford, LC, IES, Kelly Seeger, MSc, LC, IES, LEED AP, Signify Arguably, the biggest challenge we face (as an industry) is how to successfully apply circadian science to garner real, demonstrable benefit for people. As manufacturers, we are challenged with figuring out the technical specifications—the recipes, so to speak—to create lighting products and systems that deliver circadian benefit.

By Douglas Steel, Ph.D., NeuroSense The purpose of this article is to evaluate from a biological standpoint the rationale for the establishment of a Circadian Lighting standard put forward by UL under the direction of Dr. Mark Rea of the Lighting Research Center at Rensselaer Polytechnic Institute. This critique is limited in scope but also applies to utilization of the Circadian Stimulus (CS) calculator also developed by the LRC.

By Ian Ashdown Whether you call it “circadian lighting,” “biologically effective lighting,” or some other name, the principle is the same: the color and intensity of light can be used to regulate the timing of our biological clocks, or “circadian rhythms.” For architects and lighting designers, this is an opportunity to provide healthy and comfortable environments for building occupants.

By Dr. James M. Gaines Flicker and stroboscopic effect are presently hot topics in lighting, along with other subjects like blue light (subject of a recent FIRES article). A National Electrical Manufacturers Association (NEMA) standard, NEMA 77, addresses measures for temporal light artifacts (TLA), which is an umbrella term covering both flicker and stroboscopic effect (as well as phantom arrays. The NEMA metrics for flicker (short-term flicker indicator, P_st) and stroboscopic effect (Stroboscopic Visibility Measure, SVM) are both based on experiments done with many human observers, to measure average human sensitivity to flicker and stroboscopic effects.

By Eric Bretschneider, Ph.D How often do we hear about the dangers of blue light from LEDs? Such discussions inevitably include statements about "the intense blue peak" in LED lighting and the potential for damage from the massive amounts of blue light present in LED lighting. The whole argument sounds plausible enough when we look at the spectrum of a typical white LED. The spectrum below is for a typical white LED with a CCT of 4,000 K at levels that approximate a typical commercial or retail environment (400 lux). The isolated peak in the blue clearly stands out, but does it really represent a massive dose of blue light?

By Ian Ashdown, P. Eng. (Ret.), FIES Senior Scientist, SunTracker Technologies Ltd. Numerous medical studies have shown that exposure to blue light at night suppresses the production of melatonin by the pineal gland in our brains and so disrupts our circadian rhythms. As a result, we may have difficulty sleeping. It is therefore only common sense that we should specify warm white (3000 K) light sources wherever possible, especially for street lighting. True or false?

By Douglas Steel, PhD These are transformational times for the lighting industry. The cost of LED-based products has dropped dramatically. At the same time, increased sophistication and capabilities of tunable LED arrays, controls, and sensors now enable the commissioning of platforms that can precisely control light intensity, correlated color temperature, and relative spectral content.

By Ian Ashdown, P. Eng. (Ret.), FIES, Senior Scientist, SunTracker Technologies Ltd. There is a common-sense argument being presented in the popular media that since humans evolved under sunlight, our bodies must surely make use of all the solar energy available to us. Given that more than 50 percent of this energy is due to near-infrared radiation, we are clearly risking our health and well-being by using LED lighting that emits no near-infrared radiation whatsoever.