Find Out If Sunglasses Are Polarised By Looking Through Two Pairs

If you’re shopping for sunglasses and aren’t sure if they’re polarised, you can easily check by holding two identical pairs at 90 degree angles to each other.

We’ve talked about why polarized lenses are awesome, but if you’re browsing for glasses at a kiosk or market, you might want to double check the authenticity of their polarised selections. As the video above demonstrates, all you have to do is hold two identical pairs in such a way that you can see straight through a lens on each. As you turn one pair slowly to 90 degrees, your vision through the second lens should get visibly darker. If the lenses aren’t actually polarised, you shouldn’t notice a change.

You could also use this trick with most LCD smartphone screens. Just look at your phone in portrait orientation, then slowly turn it to landscape to see if you notice any change. If you can though, try to test this with a pair of glasses that you know are polarised beforehand, since not every phone screen behaves the same way.

Easy test for polarised sunglasses [YouTube via Reddit


  • Interesting trivia: This doesn’t work for the glasses used for (theatrical) 3D movies. Apparently this is because they use something called “circular polarisation” which I hadn’t heard about until I tried researching *why* this doesn’t work. I’m still not entirely clear on exactly what it is.

    The 3D movie glasses pass through light when held at right angles, but it looks a bit yellow (from personal experimentation); I’m not sure why.

  • Check the left temple of the sunglasses. You should find something like 3N or 3P or 2P or 2N. The number is the category of the lens and the N means normal and the P means polarised. Eg 3P is Category 3: Polarised.

  • An easier way to check is to just look at any reflection through the lens. Rotate the glasses and see if the reflection disappears or diminishes. That is, after all, what polarising sunglasses are for.

  • A simpler way is to simple turn the sunglasses 90 degrees while looking at your smartphone and see if it changes. Polarized sunglasses are best for when you are on the water or in the desert; otherwise they interfere with seeing anything with an LCD screen. Check out some great sunglasses at

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