The Invisible Light That’s Harming Our Health — And How We Can Light Things Better Amber Case Follow 7 min read · 4 hours ago 4 hours ago -- Listen Share
I recently spent a few weeks running a conference for a community of researchers and writers in a historic chateau in the French countryside. During this time, I also examined the history of the building and how texture, size and proportionality affected thinking in the space.
This experience turned out to be a perfect illustration of how some modern lighting choices can disrupt our experiences in places as beautiful as this.
This beautiful French chateau hosts a community of writers, artists and philosophers in the wintertime, and weddings in the summer. It’s been marvelously restored through a lot of love and hard work.
The Chateau was built in the 1650s on top of a hill overlooking a village of ~400 people in the countryside outside of Paris. During the day, all of the rooms were stunning, but at night, some of them began to feel uncomfortable.
One of the Chateau’s rooms in natural light.
In the past, this room might have been lit by the warm glow of candlelight or a warm incandescent lightbulb on a 100 year old chandelier. But now, like many historic buildings, analog bulbs had been replaced with LED lights for practical reasons; consistent brightness and reduced energy bills.
One room in particular felt worse than the others. I took my camera around to see why.
The light felt warm, but even with this warm light and beautiful interior, I didn’t feel “cozy”. I asked other participants in the room about this, and they also noted that when the light was on, the room felt uncomfortable. The camera told the story clearly:
The telltale signs of flickering lights — big bands of dark and light that show up on a camera.
The big bars of color came from modern LED lights fitted into the ceiling chandelier. My camera captured what my eyes couldn’t quite detect: thick bands of light and dark across the frame. The light wasn’t steady; the LEDs were flickering, pulsing on and off thousands of times per second to create the dimmed effect.
This explained the room’s uncomfortable atmosphere. Like many historic spaces, it had been “upgraded” with modern lighting that created an unwelcoming environment despite its warm appearance.
The truth is, most light sources flicker; very few people perceive it directly, but we still feel its effects. You may have noticed that some light bulbs emit a warm glow that somehow doesn’t feel cozy. Often, what we’re unconsciously reacting to is that subtle flicker.
The technical source of the issue is called pulse-width modulation (PWM), a method of controlling how much electricity a light source (in this case) receives at any given moment; it causes the light source to be off for a split second. Hence the flicker.
PWM is an often-used default for OLED digital displays (smart device screens, computer monitors, etc), LED lights, and some incandescent bulbs.
Flicker is all around us. We usually don’t see it, because our eyes are generally good at averaging out artificial light sources, similar to how we see a rapid series of individual images as a single moving picture. But it’s still a force that causes eye strain or discomfort.
Think of it like a soda dispenser. When you pour yourself a soda at a movie theater or fast food joint, it doesn’t usually dispense your selected brand. It’s cheaper for companies to store soda outside of the flavoring. So instead, what happens is the designated soda flavor “pulses” into the cup, mixing with the soda water.
This is more or less how we see PWM-based light — but in this analogy, our eyes are the cup! More advanced dimming systems pre-mix the light before sending it into your eyes. This greatly reduces eye-strain and makes for a much more comfortable long term experience.
And this is a process that usually happens to us during our entire waking day, forcing to process all the blinking on and off lights around us as a uniform experience. A significant minority of us — from 5% to 20% — have acute reactions to this flicker, up to and including migraines and nausea. There’s even a PWM Sensitive support group on Reddit!
Here’s a breakdown of PWM symptoms and their propensity: