Coatings and filters
UV400
Optical glossaryCoatings and filters
Full ultraviolet protection to 400 nanometers. Invisible: darkness and UV protection are unrelated properties.
Worked example · standard optics, computed
In more depth
Ultraviolet light sits just beyond violet, below 400 nanometers, in two bands that reach the eye: UV-B and UV-A. A UV400 lens absorbs both — everything up to 400 nanometers — while visible light passes as usual.
It is a property of the material or an absorber in it, and it is completely invisible: a perfectly clear lens can block all UV, and a dark one can block none. A dark lens without UV protection can be worse than no lens, because the pupil opens wider behind it.
Related terms
TintA fixed color in or on a lens. Cosmetic or comfort — a tint alone is not UV protection.PhotochromicA lens that darkens in ultraviolet light and clears indoors. Most photochromic lenses react poorly behind windshields, which block most UV.PolarizedA lens with a filter that blocks the horizontally-reflected light that reads as glare off water, roads and glass. Permanently tinted.Blue light filteringAttenuation of the blue end of the visible spectrum, associated with reduced eye fatigue on long screen days. The evidence supports comfort, not medical protection.