The Denver law office’s art collection was curated over three years, resulting in a desire to add new lights to highlight the additional pieces. The same luminaire was ordered and installed and, once viewed onsite by the lighting designers, it was visually apparent there was a color shift. Field verifying the color temperature and chromaticity coordinates confirmed there was a color shift between the “older” luminaires to the newly installed luminaires. Although enough daylighting and other sources helped to make this change indistinguishable to most observers, these situations are likely to happen more frequently.
Designers do not have as much control as they’d like over the LED diodes selected and are often assured by manufacturers there is consistency in LED diode selections for products. Questions often swirling around in designers’ heads include what is acceptable color shift and will occupants notice the visual difference? The reality is most probably will not notice, but lighting designers will.
In general, current design practice includes making sure all light sources match in color, but in the future, more projects may include different areas within a space using warmer or cooler colors, and these colors may vary throughout the day. Will occupants like spaces with varying colors, or will they even notice? Designers can help researchers understand what matters to clients/building owners because researchers rarely work with building owners.
ILLUMINANCE MEASUREMENTS
Research
Accurate illuminance measurements are a focus of the National Institute of Standards and Technology (NIST), lighting meter manufacturers and calibration laboratories. Much of this information is not easily accessible by the public, except for manufacturer literature. Illuminance meter designs may vary by detector shape and filter type, among many other design decisions by the manufacturer. The application the meter is designed for is also important because different applications, such as photography, have different needs. The variation in illuminance meter performance is why meter calibration is so important.
Reality
After collecting all the illuminance meters the authors had access to, as well as downloading numerous free phone apps claiming to measure illuminance, there were 12 illuminance meters and apps tested against each other by putting them on the same spot on an office table with no daylight in the room. (These meters and apps ranged in cost from free to hundreds of dollars.)
It was quickly apparent that phone apps relying only on the phone camera SHOULD NOT be considered reliable illuminance meters. Additionally, it was clear that yearly calibration of meters is essential so that lighting designers can verify the accuracy of their designs in the field.
The projects were designed to IES-recommended maintained light levels for the varying tasks in these offices with lighting power density values better than code requirements. Field illuminance measurements recorded during the site visits were close to the illuminance values calculated by software during the design process for each project. Illuminance will decrease over time, so designers tend to be conservative, designing projects with higher illuminance levels initially because they want to make sure there is enough light several years down the road when light output decreases because of dirt, aging LEDs, etc. It is much more difficult to add more light later, although some control systems adjust the dimming level to maintain approximately the same illuminance over the life of the lighting system.
FLICKER
Research
Flicker is a repetitive change in light output over time, and the rate at which the change happens is particularly important. Many light sources flicker, but the change in light output happens so fast that it is not perceptible to our visual system. Global interest in flicker research was reignited with the emergence of LEDs; many early LED products flickered, particularly when dimmed.
Human response to flicker varies from mild annoyance to seizures for some higher-risk populations. When LEDs are dimmed, flicker is most likely to occur, but products are improving so this is less and less likely. Researchers continue to try to better understand flicker so responses to flicker can be better understood and LED luminaires and controls can be better designed to minimize the chance of flicker.
Reality
In this time of circadian rhythms and LEDs, the idea of flicker has seemingly fallen to the wayside. Additionally, the days of flickering linear fluorescents are mostly in the past because of the switch from magnetic to electronic ballasts. But flicker is still a big deal with LED technology. Through the process of measuring flicker in these recently completed spaces, the discussion quickly revealed that to the lighting design community, flicker is not a well understood concept and there is not a current universally accepted metric to characterize flicker. Percent flicker, flicker index and SVM (Stroboscopic Effect Visibility Measure) are three metrics calculated by the meter the team used in the field.
A flicker meter is typically not a tool that most lighting design firms have on hand, and the physical act of measuring flicker requires measuring after products are installed because there are many other factors that can affect flicker, particularly in older buildings. Several steps would improve flicker understanding, including designers showing the same enthusiasm about flicker as they are currently showing with circadian rhythms. Designers should also consider using flicker meters for field verification and provide the results to manufacturers and researchers; this is critical feedback they cannot easily replicate in their laboratories. Manufacturers can help by publishing more information about flicker, and researchers can help by determining which of the flicker metrics is the most important for designers to understand. Continual dissemination of what researchers and manufacturers are learning is pivotal to the lighting design community, improving their understanding of flicker.
Final Thoughts from a Design Perspective
LED technology has done wonders for advancing research within the lighting community, placing much-needed focus on lighting and its effects on humans. These advancements allow lighting designers to create unique and beautiful spaces utilizing less energy. The seemingly increasing gap between what researchers are studying and what designers have access to and fully understand is becoming larger. The lighting industry is evolving on a monthly basis and keeping all emerging technologies, research and practice guidelines at the forefront of a design that is code compliant and aesthetically pleasing is definitely a challenge.
The lighting profession is part of a collaborative environment with designers often reaching out for help on complicated subjects. However, too often this collaborative environment does not include the research community. Hopefully, in the future as the lighting community continues to grow, researchers can be brought in as advisors for complicated lighting projects that want to go beyond normally accepted lighting practices and can help interpret and field verify results. On the flip side, researchers need to incorporate the expertise of the lighting design community as researchers design experiments and translate the research results to the broader context of the lighting community. With these types of collaborations, the gap between researchers and designers is bridged.
Attend this Presentation during LIGHTFAIR Connect
LightFair Connect is a virtual conference that will feature more than 60 hours of accredited courses and more than 50 sessions presented in seven educational tracks. It is inspired by demand for online learning that was expressed by the lighting community in the wake of the cancellation of the 2020 conference because of the COVID-19 crisis.
The authors of this article will be co-presenting “Bridging the Gap: Research to Design” Wednesday, July 22, 2-3 p.m. The session will help attendees navigate the complex world of emerging lighting research, knowing where to look and what questions to ask to apply research to the everyday design process.
Learn more and register.