An electrochromatic mirror is a rearview mirror that darkens automatically at night in response to headlights

Kind of like the eyeglasses your uncle Gus wore in the ’80s that turned into sunglasses when he stepped out into daylight, electrochromatic mirrors darken when shined on by the headlights of tailing cars. The mirrors are designed to dim like this only at night.

The electrochromatic technology usually is applied to the inside rearview mirror, where it basically saves you the trouble of flipping the mirror manually if blinded by the light. Beyond this luxury aspect, the mirrors have the added benefit of dimming proportionately to the intensity of light they read, where a manual mirror gives you only the choice of day or night.

Still, the technology is more useful in side mirrors, where I’ve seen it applied only in luxury vehicles. Why? Because if the inside mirror blinds you, at least there’s something you can do even if it’s not electrochromatic. Whereas if a Ford Expedition comes up behind you and klieg-lights your left eye through the side mirror, you have no option but to angle the mirror away, and that’s hardly a safe action. On the flip side, even the simplest side mirrors are frightfully expensive to replace; add the electrochromatic technology and heaters of the day, and that’s quite the investment out there dangling in the wind.

Information for this was taken from’s glossary, written by Joe Wiesenfelder.

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Answered by Joe Bruzek on August 27, 2008 in Glossary , How Does That Work? | Permalink

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