Polarized sunglasses and LCD screens
What do polarized lenses do to LCD screens?
Polarized sunglasses are designed to make it easier and more comfortable to see during outdoor activities. However, wearing them while trying to read an LCD (liquid-crystal display) screen can sometimes — literally — leave your eyes in the dark.
Many LCDs, such as your smartphone and tablet, use a polarizing filter to help you see the screen in bright sunlight. But so do polarized sunglasses, meaning the two can cancel each other out. This can cause your LCD screen to appear dark or completely black when you look at it.
How do polarized sunglasses work?
Polarized sunglasses are designed to block glare — overly bright light reflected off shiny surfaces such as water and snow. Natural light consists of photons bouncing in many directions. Polarized lenses filter the photons traveling in a single, uniform direction (usually horizontal).
Polarized sunglass lenses are coated with a chemical compound composed of molecules that are parallel to one another. These molecules absorb any light waves traveling in the direction in which they’re aligned, preventing them from passing through the coating.
Why you can’t see an LCD screen when wearing polarized sunglasses
LCD screens and sunglasses typically contain a polarizing filter for the same reason: to make it easier for you to see clearly in bright sunlight.
What tends to happen is that your polarized sunglasses only allow light to pass through vertically. Meanwhile, your phone screen emits horizontally vibrating light while blocking vertical light.
Your lenses and screen then counteract each other by working in opposite directions. As a result, you can wind up seeing a dark or blacked-out image.
How to see your phone screen when wearing polarized lenses
The solution is simple: Rotate your tablet or phone screen by 90 degrees. This positions your screen’s polarizing filters in the same direction as your polarized sunglasses. They block light waves traveling in the same direction, allowing other light to pass through.
Newer smartphone and computer screens have found ways to compensate for this issue. However, you may still notice a darker screen when wearing polarized sunglasses with an older model screen.
In some cases, you may need to view LCDs on an instrument panel that can’t be rotated. This can be true for boaters and pilots who need to be able to read instrumentation quickly and accurately to ensure their safety. For this reason, wearing polarized sunglasses is not recommended in these circumstances.
Polarized lenses can also interfere with your ability to see and read the displays on gas pumps and ATMs. To see more clearly when filling your tank or withdrawing money, it is recommended to remove your sunglasses when performing these tasks.
How can you tell whether sunglasses are polarized?
There are several ways to determine whether your sunglasses have polarized lenses:
- Check the labeling – Any reputable eyewear retailer (brick-and-mortar store or online shop) will provide accurate labeling on the sunglasses they offer. This allows you to tell at a glance whether the sunglasses you’re considering have polarized lenses.
- Compare two pairs of sunglasses – If you have an older pair of sunglasses, you can test them by using a second pair of shades you know are polarized. Hold the sunglasses in a way that allows you to look through both pairs of lenses at the same time. Rotate one pair of sunglasses by 90 degrees. If all light is blocked when passing through both pairs, then your older sunglasses probably have polarized lenses.
- Look at an LCD screen – You also can test your sunglasses by looking at an LCD screen while wearing them. Just remember to rotate the device 90 degrees to make sure you’re checking for a polarizing filter that blocks light traveling either horizontally or vertically.
Polarized lenses FAQs
There are several things to consider when it comes to polarized lenses and how they work.
Q. Do polarized lenses filter blue-violet light*?
A. Some polarized sunglasses also filter blue-violet light, but the amount filtered varies by lens. They're best suited for enhancing visual clarity during outdoor activities rather than screen use, as they can make some displays difficult to see.
Q. What is the difference between polarized and tinted sunglasses?
A. Tinted sunglasses help reduce overall brightness but don't necessarily provide the same glare reduction as polarized options. Both types can serve as protective eyewear by offering UV protection, but this depends on the lenses rather than their tint or polarization.
Q. What is the difference between polarized and anti-reflective?
A. Polarized sunglass lenses have a built-in filter that reduces glare from bright, reflective surfaces. Anti-reflective coatings (often called “anti-glare”) are applied to the surfaces of eyeglass lenses to minimize reflections on the lenses themselves. They allow more light to pass through and help reduce eye strain. These coatings may be particularly helpful with driving safety at night.
*Blue-violet light is between 400 and 455 nm as stated by ISO TR20772-2018. (ISO: International Standards Organization – “Ophthalmic optics – Spectacles lenses – Short Wavelength visible solar radiation and the eye, FD ISO/TR 20772”)
