By Michael Erbesfeld
Senior Program Manager
The recent publication of ANSI/IES TM-39-25 by the Illuminating Engineering Society (IES) provides a timely overview of current research, proposed metrics, and shared terminology related to the perception of flicker—including a new metric for the Phantom Array Effect (PAE), a phenomenon where multiple images appear when a flickering light source is viewed during quick eye movements.
TM-39 is not a Recommended Practice. As a Technical Memorandum, it is an informal report with a synopsis of possible problems and recommendations. While NEMA does not believe TM-39 is ready for use in product specifications or regulations today, it offers context and a starting point for further work.
NEMA recognizes IES for its leadership in publishing a Technical Memorandum that adds momentum to broader efforts across the lighting community, including work already underway within IES, NEMA, the International Commission on Illumination (CIE), Institute of Electrical and Electronics Engineers (IEEE), and the International Electrotechnical Commission (IEC).
A Commitment to Continued Collaboration
One of the biggest hurdles the industry faces is ensuring consistent measurement of TLM. Some consensus has started to form around how to measure the stroboscopic effect; however, direct flicker and PAE remain areas where additional agreement is still needed.
Several different metrics have been proposed; it is not clear which metric will ultimately be standardized and then widely adopted by the lighting community. Recent studies from the National Institute of Standards and Technology (NIST) and the International Energy Agency (IEA) show that current measurement methods can produce results that vary significantly. In some cases, measurements may differ by as much as 50 percent.1
This highlights the importance of collaboration in developing consistent, reliable approaches to measurement before any metric can be standardized and broadly used across the lighting industry.
TM-39-25 is a useful educational tool, representing progress in an important discussion. NEMA members are committed to this work and look forward to continued collaboration with IES and others to reach consensus. Together, we can advance the tools and methods needed to accurately assess TLM and support the delivery of high-quality, reliable lighting in a wide range of applications.