Have you recently bought polarized sunglasses? Polarized sunglasses cost more than regular sunglasses. It is important that you understand how your new glasses work and test sunglasses.
Many vendors sell sunglasses without sufficient polarization. It’s a waste of money if you don’t reap the benefits of polarized glasses. To remove any doubts, it’s good to know several methods to test sunglasses for polarization.
How Do Polarized Glasses Work?
Light travels as waves that vibrate in specific directions. When light reflects off surfaces, light waves form a horizontal line. To reduce glare, polarized sunglasses use a special chemical coating. This coating only allows vertical polarized light to pass through. With polarized lenses, users see drastic reductions in glare. They notice increased clarity and sharpness of detail. Polarized glasses work well in bright environments like beaches, lakes, and snowy landscapes. Check out these four videos below.
How to Test Sunglasses
At first glance, it’s not easy to distinguish between polarized and regular sunglasses. High-quality polarized glasses might appear almost the same from regular sunglasses.
Fortunately, there are many methods that you can try to test sunglasses. Each step comes with its own set of pros and cons. Some may even require you to purchase additional items. However, the variety of methods ensures you have many options to test if your polarized glasses work.
1. Visual Inspection
The easiest way to test sunglasses is to check the model itself. Most polarized sunglasses have a distinct label. This label indicates the lenses have a polarizing filter. For instance, some companies attach a temporary sticker on one of the lenses.
Regardless, please note scammers can easily print fake stickers. They attach them to counterfeit polarized glasses. An excellent way to confirm is to look up authentic models. Then, compare their labels with the items you have. Some manufacturers use anti-fraud mechanisms into the stickers. They use specific patterns, to prove their authenticity. If the sticker doesn’t look exactly like the official label, then the item is probably fake.
Other manufacturers directly etch the polarization label on the edge of the lens. It’s still possible to replicate this process with the right equipment. But, most won’t due to the higher cost and effort required for etching.
2. Test Sunglasses with Polarized Lenses
If you have another pair of polarized glasses, you can use them to test the others for polarization. To do the test, look for a well-lit area or find a sufficiently strong light source. Make sure the light levels are enough for you to see through both pairs of glasses.
Next, hold both eyeglasses by aligning them in front of you. The test sunglasses should be in front of the reference glasses. Leave a couple of inches between the two pairs. To avoid scratches, make sure to prevent the lenses from contacting each other. At this point, you should still see a darkened but distinct image through both lenses.
Look through one lens while tilting the test sunglasses by around 60 degrees. You should see a drastic darkening of the image. This indicates both pairs have polarizing filters. The image should be at the darkest if the test glasses are offset by 90 degrees relative to the other pair.
This test works because the polarizing filters sift through all light that is not polarized horizontally to the lens. Therefore, light passing through the reference glasses is horizontally polarized. The glasses being tested are offset from the reference. The polarizing filter blocks most of the light passing through the first pair, causing the image to darken. Note if there is no noticeable darkening even at the 90-degree offset angle. If so, the test sunglasses do not have a polarizing filter.
This test relies on the underlying physics of light polarization, so its results are absolute. However, the darkening might not be noticeable under low light conditions. This test works best in brightly lit areas.
3. Test Sunglasses with Reflective Surfaces
No polarized sunglasses to use as a reference? There’s a similar method to determine if you have polarized lenses. This time, you will need a mirror or another highly reflective surface. Make sure to have a flashlight or any other source of glare.
Move your sunglasses a few inches away from your face. Then, view the glare through one of the lenses. Similar to the previous test, gradually rotate your sunglasses by up to 60 degrees. Did the glare disappear at certain angles? If yes, then your eyewear likely has a polarization filter.
This technique works because any reflection tends to create polarized light. Polarized sunglasses utilize this property to remove glares and excess reflections. When the glare diminishes, the polarized light from the reflection is hitting the polarization filter. You can observe this when your sunglasses are at offset angles. You might also see uneven or spotty lighting when the reflecting surface has its own polarization filter.
Light polarization depends on various factors:
1. The illumination source you used
2. The properties of the reflective surface
3. How the reflective surface is angled relative to you and the light source.
In most cases, surfaces do not fully polarize reflected light. Hence, you can still see the light reflecting off the surface.
This test is less reliable than using a reference pair of glasses. However, it can give you an indication of how your test sunglasses will function in real scenarios. Even authentic polarized sunglasses might have undesirable effects. They may filter too much light. If you can hardly see the reflected light during this test, you might want to consider another model that can let more illumination through.
4. Test Sunglasses near Water
If you want to test your glasses in a natural setting, go to a bright location near a body of water. You can go to a pond or a river. For this test, the water should be as transparent as possible.
If you don’t have easy access to a body of water, you can use a bucket of water. Make sure the amount of water is sufficient to produce glare.
Ideally, do this test mid-morning or mid-afternoon, with you facing the sun. The goal is to get the sunlight to reflect off the surface of the water before it reaches your eyes. This arrangement increases the amount of glare you see which will help assess your sunglasses.
Wear the test sunglasses and observe how your vision changes. If you have another pair, use that as your reference to isolate the effect of the polarizing filter. If there’s a significant reduction in glare and brightness, your glasses work correctly. You should also notice the underwater surface of the pond or river. But note that the reduction in brightness should not hamper your vision.
This test is subjective. Regardless, it gives you a great way to assess your sunglasses from removing glare in real-life scenarios.
5. Polarization Test Cards
If you don’t mind spending some money, you can also opt to buy polarization test cards. These cards have a specialized surface that reflects polarized light. They allow light to interact with the polarization filter in your sunglasses. There are many variants of polarization test cards. But, most will show a specialized pattern only when you view them through a polarized lens. With the naked eye or non-polarized eyewear, you won’t see the pattern.
Polarization test cards are designed to give clear-cut results. You either see the indicator, or you don’t. You can then tell if your test sunglasses have a polarization filter. The cards are quick and easy but you will have to shell out additional money to buy them.
Before buying test cards, check first if your eyeglass model comes with test stickers. Some manufacturers bundle them with all purchases. They function in the same way as other test cards. Properly functioning test stickers are also difficult to fake. The image they carry will only change if you view them through a polarization filter.
6. Computerized Test
If you have a smartphone, chances are your screen already incorporates anti-glare technology. This technology relies on polarization mechanics. In this case, you can quickly test your sunglasses by using computerized methods.
This test is similar to how you would test sunglasses with a reflective surface. You should look through the lens during the entire procedure. As you tilt your sunglasses, you should see changes in the brightness of the image.
Alternately, you can wear the test sunglasses and look at your screen as you move your head sideways. If a polarization filter is present, portions of the screen should darken or appear black.
Conclusion to Test Sunglasses
There are various methods to test sunglasses for anti-glare effects. All of these techniques use the concept of light polarization. They can all indicate how effective your eyewear is in reducing glare. Given the cost of polarized glasses, you must test models before you purchase them. With a little caution and foresight, you can save yourself from unnecessary headaches and eyestrain.