Yesterday, LightNOW published a guest blog post by Jim Brodrick, DOE’s SSL Program Manager, on a new IEEE recommended practice on LED flicker.
As metrics, IEEE uses % flicker, operating frequency and flicker index. A graphic is provided that plots % flicker relative to the light source’s operating frequency. Color shading reveals safe and low-risk regions. Equations enable calculation of maximum flicker for a given light source at various operating frequencies.
The National Electrical Manufacturers Association’s Lighting Systems Division subsequently published its own position paper, Temporal Light Artifacts (Flicker and Stroboscopic Effects).
NEMA takes the position that the IEEE recommended practice proposes limits that appear to eliminate any chance of health or distraction effects, but that the limits may be overly strict, which could add unnecessary cost to driver electronics. Even incandescent lamps do not fall within the no- or low-risk region.
In the paper, NEMA asserts that standardization around flicker is hampered by lack of adequate metrics, and calls for new metrics. Current metrics, the paper states, do not quantify flicker correctly because they don’t fully account for the effects of both the frequency and wave shape of the light stimulus. The human eye is sensitive to both wave shape and frequency effects, and a metric or specification that doesn’t allow for them will be too strict for some cases and too lax for others.
Get the position paper free here.
NEMA is currently working to produce a new flicker and stroboscopic effect measurement standard and will define application-dependent recommendations.
