The National Electrical Manufacturers Association (NEMA) Lighting Systems Division has published a position paper titled Temporal Light Artifacts (Flicker and Stroboscopic Effects). Temporal light artifacts (TLAs) are defined as “undesired changes in visual perception induced by a light stimulus whose luminance or spectral distribution fluctuates with time, for an observer in a certain environment.”
The position paper is a response to the Institute of Electrical and Electronics Engineers (IEEE) recent standard 1789-2015 -- IEEE Recommended Practices for Modulating Current in High-Brightness LEDs for Mitigating Health Risks to Viewers that advocates for new limits for a number of applications, explains James Gaines, senior principal engineer, Philips Lighting, and chair of the NEMA Working Group on Temporal Light Artifacts. Not only might these new limits be too strict but they could also add unnecessary costs to the electronic components in LED products. Gaines goes on to say in the press statement that “…even incandescent lamps do not fall within the low-risk or no-effect regions in the recommended practices.”
The NEMA position paper argues that current TLA standardization is impeded by insufficient TLA assessment metrics. Rather, new flicker metrics and measurement methods for lighting are required. Current metrics do not calculate TLA accurately “…because they do not fully account for the effects of both the frequency and the wave-shape of the light stimulus.” The human eye is sensitive to both of these components of a light stimulus.
NEMA is in the process of developing a standard for TLA measurement and creating a set of criteria to define application-dependent recommendations. The position paper is free to download via the NEMA website.