Since 2009, DOE has conducted research on the visual phenomenon known as flicker. Flicker is defined as rapid variation in light source intensity, which can cause visual effects ranging from uncomfortable to harmful or dangerous. In response, the Institute of Electrical and Electronics Engineers (IEEE) formed an industry standards committee on flicker, co-chaired and staffed by DOE technical experts, among others. The work of this committee produced IEEE recommended practice P1789-2015 for evaluating flicker risks, and although its recommendations are incomplete for eradicating flicker, it raised awareness of this important health and visibility issue. ENERGY STAR®, the upcoming DesignLights Consortium® Lighting Quality Initiative, and California’s Title 20 all require the reporting of flicker performance and/or considering the adoption of flicker criteria. Some manufacturers appear to be giving flicker increased design priority, as evidenced by the improved performance of new product generations.
An understanding of why flicker matters and how much it varies across commercially available products is essential to proper lighting design. Specifying the right product for a given application and risk sensitivity further requires the ability to quantitatively characterize flicker. However, there is no standardized test procedure for measuring photometric flicker from light sources, and manufacturers rarely report flicker characteristics. Furthermore, no current flicker metrics are fully predictive of flicker detectability in all frequency ranges and waveforms, so it often takes multiple metrics combined with fundamental flicker frequency information to anticipate a product’s performance. More consistent waveform measurement is needed along with better metrics derived from that waveform.
Ideally, a test-and-measurement procedure would facilitate the capture of light-source intensity or luminance over time and potentially describe how to characterize periodic waveform characteristics (e.g., amplitude modulation, shape or duty cycle, frequency) using one or more metrics. Currently, DOE contributes expertise and technical support on the following committees:
- Illuminating Engineering Society (IES) Testing Procedures Committee, Method of Measuring Optical Waveforms for Use in Temporal Light Artifact (TLA) Calculations
- International Commission on Illumination (CIE) Technical Committee 1-83, Visual Aspects of Time-Modulated Lighting Systems, developing a standard for the visibility of the stroboscopic effect
- CIE Technical Committee 2-89, working toward standardized measurement procedures for the flicker waveform
THE PERFORMANCE OF FLICKER METERS
A profusion of handheld flicker meters have come on the market to help users determine in the field if flicker is occurring and, if so, whether the level is acceptable for the application in question. These meters range from simple smartphone applications to scientific-grade meters. DOE has conducted two studies of flicker meters – one on the handheld variety and the other on benchtop models – to determine how they perform and to identify any issues.
- Characterizing Photometric Flicker: Handheld Meters
A 2018 study documenting the capabilities and accuracy of eight handheld meters capable of measuring flicker in the field, compared to a reference benchtop meter.
- Characterizing Photometric Flicker
A 2016 study comparing three benchtop laboratory meters against a reference system to evaluate their performance and accelerate development of standard test and measurement procedures.
The increased availability of more affordable and easier-to-use measurement devices indicates the growing awareness of flicker by lighting technology developers, and the improved ability to address it through emerging measurement methods and recommended practices.
2019 Webinar: Metrics in Motion: Flicker & Glare
2018 Report: Characterizing Photometric Flicker: Handheld Meters
2016 Report: Characterizing Photometric Flicker
2015 CALiPER Report 22.1: Photoelectric Performance of LED MR16 Lamps
2014 CALiPER Report 20.2: Dimming, Flicker, and Power Quality Characteristics of LED PAR38 Lamps
2014 CALiPER Retail Lamps Study 3.1: Dimming, Flicker, and Power Quality Characteristics of LED A Lamps
2012 Presentation: LED Dimming: What You Need to Know
2014 Presentation: SSL Flicker Fundamentals and Why We Care
2015 Presentation: Flicker: Understanding the New IEEE Recommended Practice
1989 Journal Abstract: Fluorescent Lighting, Headaches and Eye-Strain
2015 International Electrotechnical Commission Technical Report 61547-1: Equipment for General Lighting Purposes - EMC Immunity Requirements - Part 1: An Objective Voltage Fluctuation Immunity Test Method
2012 Journal Article: Risk assessment for LED lighting flicker