Spectral Wars Episode 3: The Valley of Cyan

by | Jun 25, 2021 | News

Far away in a long-forgotten decade, lighting manufacturers battled for international market dominance of fluorescent lighting. They offered energy efficiency, enhanced color rendering, and even health benefits for some products. Today the fight for world dominance continues, using new LED weapons that are even more energy efficient, ever better color rendering, and potentially more capable than ever of making people healthier. At first, the prize was energy efficiency, but as the battle continues the true prize of human wellness has become clear. The combatants are tirelessly working behind the scenes to determine how circadian science, human physiology, and light source spectral power distributions can be finessed into manufactured products complete with detailed instructions as to how to deliver it. The battle location, known by combatants as the Valley of Cyan, will be where circadian photobiology meets roaming tribes of zealot metric warriors, disenfranchised early adopters, and woke scientific purists all fighting to develop and produce the right spectral dosing to deliver health, productivity, and wellbeing benefits to the conquered and willing.

Twenty years ago, the breakthrough discovery of the intrinsically photo-responsive ganglion cells (“iprgc cells”) in human eyes coupled with a greater understanding of the circadian system response to light set the lighting industry on its head. In a haste to capitalize on the opportunity, early adopters called their ideas “human centric lighting” (HCL) and initially promoted fluorescent retrofits using 8000K lamps. The marketing spin was based upon the false assumption that blue rich white light was the panacea for unilateral enhanced visual acuity, greater energy efficiency, and “healthy” light. The HCL movement sputtered but did not die as it scrambled on the continuing notion that duplication of natural light was as simple as lots of short wavelength light by day and little to none at night. This notion was monetized by the ease of combining LEDs of two different color temperatures and cross fading them at the proper times. Now called white light tuning, test installations were made in classrooms, senior housing, hospitals, and offices all around the developed world, which led to HCL became a marketing phenomenon that added $1 billion to the US lighting industry in 2020 alone.

Comparing the Seoul “Sunlike” LEDs to generic blue-pump LEDs at common correlated color temperatures

But white light tuning is at a critical juncture. A relatively simple combination of ordinary high and low color white LED lighting using a basic dimming system allows the lighting to have either color temperature or a mixture of both. It is presented as easy as high CCT (5000K+) for “day active” periods and low CCT (3000K or less) for preparing to sleep. Mass production is already underway and equipping the armies with weapons of all types, from downlights and troffers to special “circadian” lighting. But emerging research points to the limited amount of red and cyan, caused by low-cost, blue-based LED manufacturing practices and gives new insight into the need for short wavelengths alone for circadian relevance(1).

Until recently only a few specialized LEDs produced the spectrum of light most needed for a system wide circadian benefit. Common LEDs, even with high CRI, typically provide little light in the wavelengths we recognize as cyan between 487- 520nm. To win this war, LED lighting systems must significantly increase the amount of light in cyan and ensure a robust presence of red between 630 – 660nm as well. For projects pursing the latest version of WELL, the dramatically increased “melanopic” cyan wavelengths are a huge benefit.

There is another health-related reason for this new generation of LEDs. Australia, New Zealand and several other countries have required the use of certain lighting systems in health care settings for several decades. Codes call for the use of light sources that meet Cyanosis Observation Index (COI) requirements throughout health care and emergency facilities. Cyanosis(2) is nature’s warning sign of sepsis onset and/or imminent death and proper lighting spectrum allows staff to easily recognize it by being able to easily see the purplish-red discoloration of the skin resulting from poor circulation or inadequate oxygenation of the blood. To meet COI requirements, general and surgical light sources must be between 3300K and 5700K and have a COI value of 3.3 or less(3). This rating system ensures that personnel can visually recognize the dermal discoloration and act quickly to combat the deadly condition. And here’s the catch…. meeting COI in effect requires the presence of cyan in the light source! It is hard to detect cyanosis unless cyan is present in the light source due to the human eye tristimulus preference for simultaneous contrast, which is the tendency of a surface color to induce its color wheel opposite in hue, value, and intensity upon an adjacent color. The Aussies learned the value of such light sources a long time ago, and I wonder why we do not require them too.

A new generation of LED’s are now emerging that appear to be the spectral war weapons of choice. They have CRI of 97 or higher, high R9 and conquer the Valley of Cyan. Called “sunlike” by one manufacturer, this new battle strategy is a lamp that spectrally ensures superb color rendering, is COI compliant(4) and reinforces the human circadian system. Benefits are even achieved at 3000K. If I am designing to help my clients with the most up to date HCL tool, I will certainly be specifying this new generation of LEDs.

In closing, I wish to add that for the full benefit that HCL promises, it is not as simple as the right LEDs. There are a number of other contributing factors necessary for lighting interventions to be successful in delivering bioactive circadian and health benefits. They include daylighting, interior surface reflectivity, vertical plane illuminance, ceiling plane illuminance, spatial distribution, architectural geometry, and color temperature(5). Although these considerations and the contribution they provide have been known and discussed for several years, there is a new open access journal report that offers an excellent basis for quantifying these factors. Be sure to check out this interesting paper from Robert “SolerWalker” and “Princess” Erika Voss(5) .

May the force be with you and your cyan light saber….

(1) Spitschan, M., Lazar, R., Yetik, E., & Cajochen, C. (2019). No evidence for an S cone contribution to acute neuroendocrine and alerting responses to light. Current Biology, CB, 29(24), R1297–R1298. doi.org/10.1016/j.cub.2019.11.031
(2) Ian Ashdown, “In the Blood”, All Things Lighting, February 15, 2019.
(3) Calculated from spectrometer data of the source.
(4) In 4000K and 5000K versions
(5) Soler R and Voss E (2021) Biologically Relevant Lighting: An Industry Perspective. Front. Neurosci. 15:637221. www.frontiersin.org/articles/10.3389/fnins.2021.637221/full.

This article was originally featured in the June issue of designing lighting (dl)