A lens with a faint warm cast in a stand, a blank screen glowing softly behind it.

Coatings and filters

Blue light filtering

Optical glossaryCoatings and filters

Attenuation of the blue end of the visible spectrum, associated with reduced eye fatigue on long screen days. The evidence supports comfort, not medical protection.

Visible light runs from violet to red. Blue light is its short-wavelength end, roughly 400 to 500 nanometers, right next to the ultraviolet the eye cannot see.

Worked example · standard optics, computed

In more depth

Blue light is the short-wavelength end of the visible spectrum. Daylight is by far its largest source; screens emit much less. A filtering lens reduces part of it, either with an absorber in the material, which can leave a faint yellow cast, or with a reflective coating, which shows a bluish sheen.

The claims made for it vary widely in strength. Comfort on long screen days is the part wearers most consistently report; protection against eye disease is not what the research shows. The science page grades each claim separately, so you can see which is which.

Related terms

UV400Full ultraviolet protection to 400 nanometers. Invisible: darkness and UV protection are unrelated properties.Residual reflectionThe faint color an AR coating still reflects — green, gold or blue depending on the layer design. A signature, not a flaw.Anti-reflective (AR) coatingMicroscopic layers tuned so surface reflections cancel. More light through the lens, no bright rectangles over your eyes, no headlight starbursts.

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