Polarised vs Non-Polarised Sunglasses: What's the Difference?
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Quick answer: Polarised lenses contain a filter that blocks much of the glare reflected off flat surfaces such as water, roads and snow. Non-polarised sunglass lenses reduce the overall light reaching your eyes but don't single out that reflected glare. Polarisation is about glare, not UV, so check the UV details and the lens category separately.
What polarised lenses do
When sunlight bounces off a flat, horizontal surface such as a lake or a road, the reflected light becomes largely horizontally polarised. That reflected light is what's usually meant by glare. A polarised lens has a filter set vertically, so it blocks much of that horizontal light while letting other light through.
The result is less glare off the water and other flat, shiny surfaces. ARPANSA, the Australian Government's radiation safety agency, notes that polarised lenses are popular because they reduce glare from many reflective surfaces and help ease eyestrain.
What non-polarised lenses do
A non-polarised tinted lens cuts the overall amount of light that reaches your eyes. It makes a bright day more comfortable, but it doesn't pick out reflected glare, so a bright reflection off the water is dimmer but still there.
How much light any lens lets through is described by its lens category, whether or not it's polarised. Categories run from 0 to 4 under the Australian standard, and our guide to sunglasses lens categories in Australia explains each one.
Polarisation and UV are separate
A polarising filter deals with glare. It doesn't add UV protection on its own. The Victorian Government's Better Health Channel makes the same point: polarised sunglasses reduce glare, but they don't provide any additional UV protection. UV protection comes from the lens material, so check the UV details and the AS/NZS 1067.1 label separately. Our guide to what UV400 means covers that side.
Where polarised lenses help
- Water. At the beach, on a boat or fishing, where light reflects strongly off the surface.
- Snow. Flat, bright snow reflects a lot of light as glare.
- Bright days around flat, shiny surfaces. Polarisation targets the horizontal glare these surfaces reflect.
Every Houser lens is polarised and rated UV400, in six colours, set in a satin gunmetal metal frame. You can see the full range in metal sunglasses.
Where polarised lenses can get in the way
- Screens. LCD screens, such as those on some phones, ATMs and dashboard displays, give off polarised light. Through polarised lenses they can look dim or black at certain angles.
- Shiny metal. Light reflected off metal, such as chrome trim, isn't polarised in the same way, so polarised lenses won't remove that kind of reflection.
- Icy slopes. Some eye-care professionals caution that polarised lenses can make it harder to tell icy patches from snow.
- Flying. The US Federal Aviation Administration doesn't recommend polarised lenses for pilots, because they can reduce the visibility of cockpit displays and hide the glint of light off other aircraft.
How to check if sunglasses are polarised with a phone or laptop screen
LCD screens use polarising filters, so the light leaving them is already polarised. That makes a screen a handy test.
- Open a white page or a blank document on a laptop, monitor or phone, and turn the brightness up.
- Hold the sunglasses a short distance in front of the screen and look through one lens.
- Slowly turn the sunglasses a quarter turn (90 degrees) while you keep looking at the screen.
- If the lens is polarised, the screen goes noticeably darker at one angle, sometimes close to black. If the brightness barely changes, the lens probably isn't polarised.
Not every screen gives off polarised light in the same way. If nothing changes, try the test on a different screen, such as a laptop or computer monitor, before you decide.
If you already own a pair you know is polarised, there's a second check. Hold one lens of each pair in front of the other and turn one pair a quarter turn. Two polarising filters at right angles block most of the light, so the overlap goes dark.
Which should you choose?
If you spend time near water or in the snow, polarised lenses cut the reflected glare that a plain tint leaves in place. If you read LCD screens outdoors a lot, or you fly, a non-polarised lens may suit you better. Either way, check the lens category on the label for how dark the lens is, and look for the AS/NZS 1067.1 label.
FAQ
Do polarised sunglasses block more UV?
No. Polarisation reduces reflected glare. UV protection depends on the lens material and is a separate property, so check the UV details and the AS/NZS 1067.1 label.
Can I still see my phone through polarised sunglasses?
Usually, but some LCD screens look dim or black at certain angles. Turning the phone a quarter turn often brings the picture back.
Are mirror lenses the same as polarised lenses?
No. A mirror finish is a reflective coating on the front of the lens. Polarisation comes from a filter built into the lens. A lens can have one, both or neither. Houser's Silver, Red, Purple, Blue and Green lenses are polarised with a mirror finish, and Smoke is polarised without one.
How can I tell if my sunglasses are polarised?
Look at a bright LCD screen through one lens and slowly turn the sunglasses 90 degrees. A polarised lens makes the screen go much darker at one angle.