What Is Blue Light, Really? Screens, LEDs, and the Sun
"Blue light" gets blamed for everything from tired eyes to bad sleep — but most people have never been told what it actually is. Here's the plain-English version.
It's just one slice of visible light
Light travels in wavelengths. The ones your eyes can see run from red (long wavelengths, lower energy) to violet (short wavelengths, higher energy). Blue light sits near the high-energy end — roughly 400 to 500 nanometers. It's sometimes called "high-energy visible" light for that reason.
Crucially, blue light is completely normal. It's not exotic or artificial. You've been bathed in it your whole life, because the single biggest source of it is the sun.
Where blue light comes from
The sun. Daylight is overwhelmingly the largest source of blue light you'll ever encounter — vastly more than any screen. That daytime blue light isn't a problem to avoid; it's actually a signal your body uses to stay alert and keep your internal clock on schedule.
LEDs. The energy-efficient bulbs in your home and office produce more blue light than the old warm incandescent bulbs did. It's a smaller dose than sunlight, but it runs late into the evening when sunlight wouldn't.
Screens. Phones, tablets, laptops, and TVs all emit blue light via their LED backlights. The amount is real but modest — far less than stepping outside at noon. What makes screens notable isn't the intensity, it's that they're inches from your face, often in the dark, often right before bed.
So is it good or bad?
Both — it depends on timing. Blue light during the day helps you. Blue light late at night can nudge your body clock and make it harder to wind down. That single idea — timing matters more than the light itself — is the key to everything else in this series.
If late-evening screens are part of your routine, filtering some of that light is a sensible move. Every pair in our Glasses Collection is UV400, so they also block the UV you can't see when you're out in actual daylight.