Human-centric lighting: The effects of flickering

There are many health advantages to installing lights that are flicker-free. When it comes to human-centric lighting, the aim is to design a scheme that benefits the occupants and, where possible, includes artificial light sources that are similar to natural light. Picture a stereotypical gloomy office space and your mind will no doubt conjure images of rows of cubicles, clinical white surfaces and at least one incessantly-flickering ceiling light. Even the thought of that hypothetical light being replaced is relieving. But what is it about continuously blinking lights that are so annoying? Let’s take a look at what flicker is, how our bodies are affected and some countermeasures.

Flickering light occurs when there is modulation, instability or variance in a light’s intensity or colour. Sometimes the variance is perceptible, like in our imagined office space, but flickering can also be imperceptible to the human eye, yet still impact us detrimentally. Regardless of whether we realise it or not, our eyes are constantly working to adapt to the continuous variation in colour and brightness. Numerous studies have proven that flickering light can have negative physical and mental impacts, such as lower concentration, dizziness, migraines, eye strain and fatigue, while flicker-free lights promote concentration, productivity and clarity. Professor Arnold Wilkins at University of Essex has researched lighting for decades, noting that ‘one study found incidences of headaches and eye strain in a London office halved when the fluorescent flicker was reduced’ (source link).

Lumi Lightings

Aid productivity while working from home with conscious lighting choices. Image courtesy of Ridgewater Homes.

What about wavering of light that occurs but is seemingly unnoticeable? If it’s undetectable, is it possible to figure out whether a light is actually flickering? It helps to think about a strobe light, similar to what would be used in a night club, blinking so rapidly that it appears as though there’s no blinking. If a basketball gym is fitted with lights that flicker at a high rate, when everyone is moving at a normal pace the flickering may not be noticeable. However, when a ball is thrown across the room it can present a distracting, near-stroboscopic effect. Our brains work harder to piece together this fast strobe in order to perceive a steady light source, but motion will appear slowed down or distorted, inducing a very fatiguing experience. 

The at-home version of the hurtling basketball is to hold a pencil by its tip and waving it quickly back and forth in front of a window with natural light. Next, do the same action under an artificial light that is switched on and compare the movement of the pencil. If the pencil appears as a blur, as it will under natural light because the sun is steady, there is no flicker present (or it is within a normal range). However, if there are apparent gaps between the pencil this is a strobe-like effect. Another quick way to check is to hold a smartphone camera up to the light source. If black bands move across the screen, this indicates flicker.

flicker indicator | Lumi Lighting

Left: Visual gaps between the pencil’s movement indicate flicker. Right: A blur of movement from the pencil conveys a steady light source.

It’s important to note that all types of lighting products can have flicker; incandescent, fluorescent, halogen and LED. When dimming a light, flicker may be more obvious. Generally, good quality luminaires will have minimal modulation. However, it’s possible to purchase specific flicker-free products. The remedy is to install good quality flicker-free or low-flicker lights, not only in workplaces and commercial spaces, but also in rooms of the home where activities require concentration such as the kitchen or home office.

Vega downlight | Timbre downlight

Amphis has a selection of flicker-free products. Left: Vega downlight series. Middle: Cambio downlight and step light series. Right: Timbre downlight series. 

If we imagine that office and its irritating light again, the ideal solution would be to install good quality flicker-free lights and to allow natural sunlight into the space to mitigate any flicker. (And let’s add some art or colour to the walls to break up the clinical white.) By consciously considering how we build our spaces around us, we not only reduce negative effects of poor choices but allow the positive effects to strengthen and keep us healthier.