Flicker Free Monitors Are
Flicker Free AE Is
Whether noticed or not, light flicker refers to the change of visible light intensity with respect to time. While a user may not be aware of the flicker, it can cause a number of issues, including eye strain.Digital Anarchy Flicker Free AE is a powerful new way to deflicker video.The program solves an issue that's common for many types of video footage, be it from lights/electricity and cameras being out of sync, time lapse or slow motion (high frame rate) video.Everyone has experienced light flicker. A typical monitor adjusts its brightness through flickering, introducing periods of low light between higher brightness. Flicker-free monitors are specially designed to produce a single continuous light source.
Flicker leads to negative health consequences including headaches and dizziness. Flicker categorises lower frequency, higher-impact light modulations that are readily perceptible by most occupants. Within TLA there are two subcategories: 1) Flicker and 2) Stroboscopic Effects. The lighting industry uses a broad term, Temporal Light Artefacts (TLA), to describe this light behaviour.
LEDs cannot be powered by AC voltage on their own. Typical powerlines provide alternating current (AC) voltage (a sinusoidal waveform with a typical frequency between 50 and 60 cycles per second, or hertz (Hz)). Although flicker manifests itself visually in light output, flicker actually starts as a function of voltage. Instead, flicker is introduced by the power delivery, conversion, and control system to which the LED is coupled.
Depending on the dimming system and its compatibility with the luminaire, additional flicker characteristics may appear - especially when operating at dimmed light levels. For example, it is very common to see flicker frequencies of 100Hz in European markets and 120Hz in North American markets, since those markets operate on 50Hz and 60Hz mains frequencies respectively.Beyond power conversion, the other key source of voltage-induced flicker occurs when an LED lighting product is dimmed. In most cases, the power supply will return a flicker frequency at twice the line frequency due to how the sinusoidal power is corrected, or rectified. This conversion process is handled by the power supply.
This conversion successfully accounts for both frequency and amplitude, creating a more comprehensive representation of the perception of light flicker. Specifically, these "perception metrics" rely on a Fourier transform of the light output to convert it from time domain to frequency domain. Fundamentally, a successful flicker measurement needs to account for three critical characteristics: the magnitude, frequency, and waveform of the light modulation.The latest flicker measurement techniques, including stroboscopic effect visibility measure (SVM) and flicker perception, have a critical difference from Flicker Index and Flicker Percentage.
Other metrics, such as IEEE's PAR1789-2015 standard, expand the frequency range to 1000Hz to account for stroboscopic effects as well. Some of these metrics, such as Flicker Perception, limit the frequency range to what would classify as flicker, typically <120Hz. While empirical tests can introduce subjectivity, it allows a direct comparison of light sources against each other and often makes selecting light sources easier. These frequencies can be weighted against empirical human perception test results to determine the risk of negative impact on human occupants. To create a meaningful score, flicker perceptibility metrics compare the fundamental frequencies with empirical data surrounding human impact.
The two critical paths for eliminating the impact of flicker, rather than intrinsically flicker itself, are lowering the modulation percentage and increasing the frequency. Instead, the goal should be to eliminate the harmful impacts of flicker and stroboscopic effects in the environment in which the luminaires are installed. The language used should be changed and "flicker-free" statements, whether from luminaire manufacturers or power supply and driver manufacturers, should be challenged. This is especially true of any luminaire that is powered over AC mains - the filament will produce a measurable flicker as it reacts to alternating current supplied to it. Almost all light sources, whether a candle, an incandescent bulb, or an LED luminaire, exhibit changes in light output with respect to time and therefore - flicker. While this labelling might ease some anxiety about LED technology adoption, these statements can be misleading.
Flicker How To Measure It
Chasing the "flicker-free" luminaire is not a worthwhile endeavour and could end up costing more than the lighting application requires. By understanding the nature of light flicker, how to measure it, and marrying the lighting design to the desired application, proper illumination can be realised. Light flicker, whether visually detectable or not, can create problems for occupied spaces. When evaluating the merit of a luminaire's flicker claims, look for both a modulation percentage and a frequency, as those two pieces together will provide the clearest indication of flicker performance.Lumenpulse relies on flicker studies to understand the characteristics of the light output and to ensure the highest quality light delivery in all applications. In all cases, flicker treatment involves design tradeoffs like cost and fixture size - generally greater flicker reduction requires more electrical components and higher fixture costs.
Flicker will continue to grow in importance as more human impacts of artificial light are studied and specified - investing in a quality flicker metre that can output the right flicker measurements and using the metre as a tool to make design decisions, mockup evaluations, and product qualifications is a key step for any specifier. This includes fully understanding any compliance requirements, for the space - WELL Standard, for example, has flicker requirements listed.
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