Apparel & Accessories

Zinn test: Sunglasses tested for UV, polarization, and clarity

Polarized, UV protection, lens distortion — what do all these terms mean when it comes to buying sunglasses? And do they even matter?

Member Exclusive

Become a member to unlock this story. Get 25% off during our 12 days of giveaways.

Join

Already a member?

Sign In

While most reviews of sunglasses touch upon the fit, function, and feel of each pair, you won’t find that here. Rather, this is a lab test of some properties of the lenses of some of the most popular pairs of sunglasses on the market. As consumers, we’re often left to interpret and trust the data each individual brand gives us regarding the efficacy of their lenses. So I put those lenses to the test with a unique testing apparatus. Here’s what I found out.

Related: 

Decades ago, an Oakley PR representative brought into the VeloNews office an apparatus with two lasers mounted roughly parallel to each other and a few centimeters apart. He aimed the lasers so both beams converged on a single spot on the wall across the room. He put sunglasses of various brands in front of the lasers. Except for the Oakley glasses he brought, which maintained the two lasers focused on a single point, all of the others bent the beams so that the single spot split into two red spots on the wall. You can find this Oakley Optics Laser Lens Clarity Test on YouTube.

The Oakley rep claimed that, due to Oakley’s 1989 discovery of and patent on XYZ lens tapering of curved lenses in vertical, horizontal, and thickness directions (X, Y, and Z directions), simultaneously, other brands cannot duplicate this non-bending of light beams. He further claimed that there would be a greater strain on and damage to the eyes behind non-Oakley glasses since they would be doing extra work to resolve a distant object into a single image.

Over the years, I have ridden, skied, rafted, and driven with many different sunglasses, including Oakleys. As I never particularly noticed a difference in eye strain between brands, and since my eye doctor often has called my eyes “lusciously healthy,” I have often wondered how much difference a brand makes. I replicated this test at home since labs I normally might use are unavailable due to the coronavirus pandemic.

I first asked my eye doctor, also a lifelong cyclist, what characteristics of sunglasses he thinks make the most difference for eye health. He replied that the most important property is the complete blockage of incoming ultraviolet (UV) light. He also thought that polarization was important to reduce eye strain from glare off the road. He thought that it was not a big deal how glasses did on either the laser beam deflection test described above, or the Oakley “Scope Testing for Lens Clarity” video showing crispness of “NBS test target” lines projected through sunglass lenses. Still, it seems that it would be preferable to not have your eyes correcting for distortion — hence this test.

Stopping Ultraviolet light

To keep your eyes healthy, believe my eye doctor; the blocking of UV is paramount. Being of higher energy and shorter wavelength than visible light (and longer wavelength and lower energy than X-rays), ultraviolet radiation is invisible to the human eye and is characterized by a wavelength between 10 nanometers (1 nm is one-billionth of a meter) and 400nm. Visible light doesn’t suntan or sunburn human skin (or cause skin cancer); only UV light does that.

Short-wave ultraviolet light sterilizes surfaces that it hits and damages DNA. Earth could not support life on land if most UV light was not filtered out by the atmosphere. The highest-energy, shortest-wavelength (‘extreme’) UV between 10nm and 121nm ionizes the air it passes through and never reaches the ground.

Ozone in the Earth’s stratosphere absorbs the 100-279nm UVC (put out by electric welding arcs, UVC frequently damages the skin and eyes of welders) and most medium-wavelength (280-315nm) UVB light (which forms vitamin D in humans and other land vertebrates). UVA (315-400nm), a.k.a. ‘near-ultraviolet’ or ‘soft UV,’ passes through the ozone layer and thus must be blocked by sunglasses to avoid eye damage; it is visible to birds, insects, and fish, and is also emitted by the fluorescent ‘black lights’ you loved as a kid.

UV damage builds up over time and is irreversible. Exposure to UV light increases the risk of cataracts, macular degeneration, photokeratitis, pterygium (conjunctiva), skin cancer around the eyes, corneal sunburn, and ocular melanoma.

Good-quality, UV-blocking cycling sunglasses, including all of the glasses in this test, block 100 percent of UVA and UVB rays up to 400nm (UV 400 Protection). In fact, according to Joe Earley, CEO of Tifosi, polycarbonate lenses, widely used in cycling glasses due to being shatter-proof, block 100 percent of UVA and UVB rays — even clear lenses.

Some brands even reflect this in their names; Uvex is an acronym for ‘UV exclusion.’ UV blockage is not a given with lenses, even if they are glass; a clear glass window blocks UVB and UVC, but it allows UVA to pass through. If you wear sunglasses you bought in a gas station or from a street vendor, UV protection may be lacking; be aware that UV protection is unrelated to lens darkness and tint.

Polarization

Light waves coming from the sun vibrate in all planes transverse to their direction. By contrast, light reflected off horizontal surfaces such as roads, water, or snow (i.e., ‘glare’) becomes ‘polarized,’ meaning the waves are only vibrating in the horizontal plane. Polarized sunglass lenses have a vertically-oriented filter, which only allows vertically-vibrating light through. Think of rolling a hula hoop through a wooden picket fence made of separated, vertical pickets; just as the fence blocks horizontal hula hoops, polarized lenses block horizontally-vibrating light waves.

You can check if your glasses are polarized by holding them up to your computer screen, which emits vertically-vibrating light. Holding the glasses horizontally in front of the screen, the lenses are the color of the lens tint. Rotate them vertically; if the lens is polarized, it turns black, letting almost no light through.

I checked all of these sunglasses for polarization, and, as advertised, only the bifocal Dual Eyewear SL2 Pro X Polarized, and the Polarized Green lens of the Shimano S-Phyre X, are polarized. Why wouldn’t the other glasses be polarized, since they would cut glare reflected off of the road? Well, there are benefits and liabilities to polarized lenses for cycling. Yes, they cut glare and allow the eyes to rest more on a brightly-lit road. While that is fantastic for fishing (seeing the fish rather than the glare on the water) and driving, there are some people who should not wear polarized lenses, and cyclists benefit little.

Pilots don’t wear polarized glasses, because they might miss light glinting off the wings of a distant airplane. Also, the covers of some of their gauges are polarized, and tipping the head might turn them black. Skiers and snowboarders may not be able to judge the conditions of snowy terrain they are approaching since brightness will change when their head tilts. Glare helps to see contours better, important in mountain biking and sometimes on the road as well. Polarization can make seeing your Garmin harder at some head angles when the polarization of both the glasses and head unit aligns. Any time you add more layers (or more curvature) to lenses, distortion is a by-product.

In cycling, polarized lenses can cause confusion about whether the road is wet or dry. When riding toward the sun with polarized lenses, the road not only appears darker than without polarized lenses, it also often appears to shimmer, particularly darker sections like wheel ruts and recently-patched sections of asphalt. It can look like the road is wet in those areas. Ignoring the wet look could lead to a surprise in a corner that actually is wet.

Laser Procedure

I got two little lasers pointers designed to drive cats mad chasing a red spot. I drilled holes to fit those lasers through a block of wood at eye-width apart. I rounded the vertical edges of the block and installed one screw in front and two on the sides to support glasses the way the nose and ears would. With adjustment of some aiming pins, I can dial in the lasers’ directions so that both beams land on the same spot on a projector screen on the other side of the room. I then placed various sunglasses on the block in front of the lasers and measured the spacing between laser spots for each pair of glasses on the projector screen 15.5 feet away.

sunglasses testing apparatus
The testing apparatus. Photo: Brad Kaminski

This stemmed from an Oakley test, and while Oakley Sutro Origins glasses indeed maintained a single laser spot on the screen, five other sunglasses also did the same. “Light bends toward the thickest part of the lens, so in order for a curved lens to not bend the light, you need it to be taper-corrected—thicker in the middle and thinner toward the edges,” says Jamie Oman, CPO of eyewear for 100%, who worked at Oakley for many years. Oman further explains that Oakley’s patents on this correction, which it calls “XYZ technology”, have expired.

A couple of those glasses that also didn’t deflect the beams have lenses from the 174-year-old German lens maker, Carl Zeiss AG; both the KOO (Kask) Open and POC Aspire Clarity glasses feature Zeiss lenses. Given that most glasses separated the red spots on the screen, it is quite impressive when you drop a pair of glasses over the lasers and the spot stays unchanged. Clearly, Rapha, Tifosi, and Rudy Project also went to considerable trouble to achieve that, as their Pro Team, Sledge and Maskeryna SN01 glasses, respectively, joined the above-mentioned Oakley, KOO, and POC glasses in not bending the beams.

Zinn sunglasses test
Sunglasses testing apparatus. Photo: Brad Kaminski

Another interesting result is that the only glasses in this test that achieved no beam deflection are ones with a single, “shield” lens. All of the glasses in this test that have two separate lenses (which generally have more curvature than shield lenses) separated the laser beams, including a pair of Oakley Jawbones (both the dark mirror lenses and the yellow ones I had never installed before) that I’ve been wearing for years. The curvature of those shield lenses that didn’t deflect the beams vary from the POCs and Oakleys, which are flat vertically, to increasingly 3-dimensional curvature from the Raphas to the Tifosi Sledges to the KOO Opens to the Rudy Project Maskeryna SN01s, which has the most curved lenses.

Lasers hitting a blank wall
The lasers shoot a beam at a blank white wall. Photo: Brad Kaminski

People with a very wide head actually might not have any image deflection when wearing some of the glasses that didn’t achieve zero deflection in this test. Cycling glasses are highly curved to block light and wind, and flatter lenses have less distortion. Simply pulling the earpieces wider apart while in front of the lasers, thus flattening the shield lens or bringing the two separate lenses close to being in the same plane, brings the two laser dots on the screen together.

Some took a lot more pulling than others, and if the deflection was over 20mm in this test, even having a head shaped like a pumpkin won’t bring the dots together. So, even if Peter Sagan had won both the green jersey and 10 stages in the Tour this year, his head wouldn’t have gotten big enough to get 100% S3s in this test to converge the laser dots down to zero from 26mm apart.

 

Eye Chart Test

Testing sunglasses
Testing sunglasses against a white backdrop. Photo: Brad Kaminski

While looking at all of the Oakley tests posted on YouTube, its projection of an NBS test target through glasses onto a screen also intrigued me. The idea is to distinguish the narrowest black and white lines the eyes can. The NBS target’s lines are organized in groups of three, incrementally decreasing in length, thickness, and spacing, from 3.6 lines per millimeter to 20 lines/mm toward the center from the bottom and right side of the square pattern, and from 3 lines/mm to 17 lines/mm coming in from the top and left side.

In the YouTube video, when an Oakley rep places unnamed competitors’ glasses over the projector, they blur the NBS line pattern. The Oakleys, however, only darken it.

For decades I have done daily eye exercises, focusing repeatedly back and forth on distant and close items. Rare for somebody over 60, I have 20/20 vision and am also able to read the paper without reading glasses. I don’t know how much of this is thanks to the care I take with my eyes, including consistently wearing sunglasses on sunny days, and how much is thanks to genetics. Either way, I have a 20/20 baseline from which to work.

I tried to distinguish optical clarity by posting eye charts 20 feet away across the room and looking at them through all of the glasses. I have no way of judging if my eyes were correcting for lack of clarity in the lenses; all I can say is on which line I could read all of the letters.

Interestingly, the only determining factor I could discover for whether I could read all of the letters on the 20/20 line or only the bigger letters on the next line up was the darkness of the lens. With clear and lightly-tinted lenses on any glasses, I could read all of the letters on the 20/20 line (some glasses came with multiple lenses). With dark lenses, no matter how they had done on the laser test, I could only read all of the letters on the 20/25 line, not the 20/20 line.

Part of Oakley’s YouTube Lens Clarity video had another participant looking at the NBS pattern through a competitor’s glasses. He could distinguish the lines as well as with the Oakleys, despite the fact that those glasses subsequently blurred the image when placed in front of the projector. The comment by the Oakley rep was that the eye could correct for the lack of optical clarity of the lens but that it would come at the cost of eye strain.

Analogous to Oakley’s projection of an NBS test target through the glasses, VeloNews’ photo editor, Brad Kaminski, photographed the same NBS pattern from 20 feet away through every pair of glasses and their extra lens(es), if any. With the camera on a tripod, using a 200mm lens at f/8 1/80th second shutter speed and evenly lit with two softboxes at 45-degree angles, he focused on and photographed the target with nothing in between. He left all of the camera settings the same and took a photo through every pair of glasses and spare lenses.

Eye chart
Here’s what the eye chart looks like with no sunglasses between the camera and the chart. Photo: Brad Kaminski | VeloNews.com Photo: Brad Kaminski

I blew each photo up on the computer screen until the test target filled the monitor window from top to bottom. I recorded whether I could see any light between the lines at 7 lines/mm, 8.6 lines/mm, 10 lines/mm, 12 lines/mm, etc. On the photo of the test target without any glasses in between, I could distinguish the full 20 lines/mm.

As with looking at the eye chart through the various sunglasses, the darkness of the lens affected how clearly I could see the target lines. If the glasses came with multiple lenses, I could generally see more lines with the light-colored and clear lenses than with the dark ones.

Unlike with the eye chart, however, the photos were much blurrier with some lenses than with others. With each lens, I recorded how many lines/mm I could distinguish on either the top or the bottom and on one side or the other. For instance, “14B,8.6S” means that I can distinguish down to 14 lines per millimeter on the bottom, while 8.6 lines per millimeter is the maximum number of lines I can distinguish on the sides. The higher the number, the less the distortion (blurriness).

In general, the glasses with a single shield lens have more curvature on the sides than top to bottom. That tended to show up on the photos as more distortion side to side than top to bottom; I could generally see more lines/mm top or bottom than on the sides. Some coatings and polarization may have affected it as well, whereas photochromic lenses, whose darkness increases under higher light intensity, seemed to have minimal distortion.

Bolle chart
The chart as seen through the Bollé Vortex glasses. Photo: Brad Kaminski

With the ability to see the maximum 20 lines/mm on the bottom and 17 lines/mm on the sides, the glasses with the least distortion were the Bollé Vortex with an amber photochromic lens. The glasses with the most distortion were either the 100% S3 with gold mirror lens (10 lines/mm bottom; 5 lines/mm sides) or the Rudy Project Cutline gold mirror lens at 7 lines/mm bottom and 7 lines/mm sides (possibly due to the gold mirror coating and adhesive causing distortion?). As on the laser test, the most surprising were the Rudy Project Maskeryna SN01, which have lots of curvature side-to-side and top-to-bottom, yet, at 14 lines/mm bottom and 17 lines/mm sides, was only surpassed by the Bollé Vortex (and equaled by the Tifosi Aethon photochromic lens).

Rudy Project Cutline
Rudy Project Cutline with Gold lenses. Photo: Brad Kaminski
100% S3 chart
100% S3 Chart. Photo: Brad Kaminski

The Upshot

Graph results
Click to enlarge.
Photo: Heidi Carcella

So, what can we come away with from these tests?

Firstly, all of these glasses protect the eyes from the most dangerous onslaught to them other than impact, namely UV light. Secondly, there are benefits and detriments to polarized lenses and no compelling reason why they should or should not be in cycling glasses. Thirdly, Oakley is not the only company whose lenses don’t bend light coming into the eyes, and not all of its glasses pass the laser test.

Finally, image crispness in the photos taken through the lenses at an NBS test target depends on the amount of light coming through the lens (dark vs. light or clear lens), lens curvature, and lens construction.

Some other details

I don’t want to minimize any technology in any of these glasses. They are all quality sunglasses and have numerous well-thought-out features in the lenses, the frames, and the extras they come with. That said, there are a couple of the glasses that have particularly unique features that I noticed while riding.

Dual Eyewear glasses are bifocal; they magnify along the bottom edge of the lens. This can be a big deal for some riders who depend on reading glasses scattered around the house. I’m fortunate to be able to read my phone, computer, books, and newspapers without reading glasses except in low light. My wife, however, depends on reading glasses, and when outside she only wears Dual bifocal sunglasses. Riders with difficulty reading their bike computer might appreciate them. The magnification area along the lower edge of each lens is available in 1.5, 2, and 2.5 diopter power.

The Oakley Sutro Origins glasses don’t fog up when wearing a Covid mask, thanks to big vent holes along the top edge of the lens. I have a pronounced brow ridge that contacts the top edge of virtually any glasses I put on, blocking airflow up and out when air is shunted up under the glasses from the top of a mask, and other glasses tend to fog up on me with a mask. Oakley is owned by EssilorLuxottica SA, the largest optics company in history.

Bottom line

With the best performance overall on both tests, lasers and NBS test pattern, drum roll, the Rudy Project Maskeryna SN01 takes the cake. However, their light tint, which helps on the NBS clarity test, makes them not great for riding on bright days, and, since those are no longer made, they are disqualified anyway. That leaves the Rapha Pro Team as the top performer overall, followed by the KOO Open and then the POC Aspire. Of course, these being sunglasses, your choice of style and fit will also be critical, and you can’t go wrong with any of them.


Manufacturer responses to this test

After completing my testing, I reached out to various manufacturers whose sunglasses I included in the study. Here are some of the responses I got about the value of the testing as well as the reasons for some of the features included in various glasses.

From Jerry Bedingfield, who manages Smith’s lab and lens development:

Smith with orange lens
Smith Ruckus sunglasses with orange lenses. Photo: Brad Kaminski

“Laser Lens Clarity Test: It only proves that light is managed as it passes through the lens material, the goal is to not redirect the light creating distortion for the user. The test was patented and should have expired. Smith/Ruckus lenses utilize lenses with Optics, meaning the thickness of the lens and the curvature are such that light moves through the lens as if it was not there. The effect is no distortion. This same lens technology is used on all of our goggles as well as sunglasses, and shields.

Scope Testing for Lens Clarity: Regarding lines of resolution, this is a test also used by Smith, and again all lenses comply and test favorably against Oakley products. The test does test clarity, but also can be affected by tints, so results should be considered as an indication of clarity. Polycarbonate lenses usually test similarly if from a similar quality of Polycarbonate. Polyurethane lenses test better.

Overall, with confidence, the Ruckus is first class in the cylindrical lens category. Its clarity and optics are significantly better than the competitors’ offerings. Once you add ChromaPop, it should be unequaled. Smith has extensive testing capability in-house at the Smith testing lab today; that is not the case at Oakley, and Smith meets the rigorous requirement for tactical and PPE use.”

From Luis Viggio, CEO of Dual Eyewear:

Dual SL2 Pro X
Dual SL2 Pro X glasses with grey lens. Photo: Brad Kaminski

“Those tests that Oakley is talking about (are) nothing special. Anyone that specializes in ANSI safety can pass those tests. All PC lenses are designed with varying thickness and allow light to pass through without distortion. It is why on an 8C Based PC lens we ask clients if they need their lenses to be “de-centered”. It is also why flat TAC polarized lenses give distortion when assembled onto 8C rimmed frames.

As for lens tapering, that is nothing special, either. It’s just explaining indirectly how polarized lenses work. Polarized lenses are laminated in a vertical pattern so that it allows vertical light to come in, but blocks out horizontal light that comes from light bouncing off flat surfaces (known as glare).

Lastly, light will need to pass through your lens, otherwise you can’t see anything. That’s why you have UV protection to block out the rays at 400+.

The video actually does a good job explaining what some of those tests do. But they are careful not to say they own patents of any kind.

Our glasses are FDA-approved because they are listed as medical devices. We have to include testing data on every shipment; if not, the FDA does not let the shipment in.”

From Joe Earley, CEO of Tifosi:

Tifosi Aethon
Tifosi Aethon sunglasses with grey lenses. Photo: Brad Kaminski

“For sports like cycling, consumers want curved, shatterproof lenses. Dual lenses are often 8-base or 9-base (the bigger the number, the higher the curvature). Our Sledge (shield) lens is 7-base side-to-side and 4-base top-to-bottom, whereas our Aethon is 7-base both side-to-side and top-to-bottom. The greater the curvature, the greater the distortion. Sunglasses sold at gas stations are often acrylic or TAC (triacetate cellulose) lenses, which, unlike polycarbonate or Trivex lenses, are neither shatterproof nor 100-percent protective against UVA and UVB rays.”

From Rudy Project North America:

“We are not in a position to comment on Oakley’s technology or the specific tests that they conducted. We are confident that our premium lenses will perform at least as well for the reasons stated below.

As a manufacturer of premium sports eyewear, Rudy Project understands and addresses optical performance challenges inherent in lenses mounted in high wrap frames. We utilize our own lens technology to optimize optical performance and minimize prismatic lens aberrations/distortions encountered when the eye rotates to an off-axis gaze in a high wrap frame.

Regarding lens materials, Rudy Project offers both polycarbonate and ImpactX-2 lenses in its eyewear. ImpactX-2 refers to a proprietary formulation of Trivex material which offers superior visual acuity to polycarbonate. ImpactX-2® lenses are guaranteed unbreakable for life. ImapctX-2 lenses employ breakthrough photochromic semi-rigid molecular properties formulated exclusively for Rudy Project to ensure unique light management and unparalleled eye protection from sun rays and atmospheric elements. Getting dark from low to high light transmission within a few seconds and reaching a custom color from an initial clear state, ImpactX-2 unbreakable lenses enhance contrast and improve visual acuity and depth perception. ImpactX-2 lenses are 16 percent lighter than CR-39 and 10 percent lighter than polycarbonate; they have lower internal stress and chromatic dispersion than polycarbonate, resulting in sharper images, higher definition, reduces “rainbowing”, and more visual comfort.”

From Rapha:

“First of all, both tests in the videos correlate to the Z87.1 standard, which all of our lenses comply with (when they are brand new).

-The laser beam/prismatic lens test

-The line target/definition test

According to our lens supplier, we were able to make our lenses just as optically correct, if not more, than all other players in the market.

Since our Toric lenses similar to Oakley’s, vs. other brands are based on a spherical shape, they are not only tapered in vertical and horizontal but in multiple directions.”

From 100%, a San Diego-based company founded by Ludo Boinnard, a French former motorcycle champion:

Jamie Oman, CPO of eyewear for 100% was at Oakley for many years. He said a Google video call with me, “Those (Oakley YouTube) videos are the ANSI Z87.1 test and are valid tests. They are the optical standard that we and other sports sunglass manufacturers adhere to, and the US military has adopted them as well for its optical standard. They show that the lenses are within plus or minus .0625 diopter, which is a very tight standard. The laser test is essentially a prism test, showing how much the lenses bend the light and how much magnification or minification they cause. When I was at Oakley, I built those tests.

Light bends toward the thickest part of the lens, so in order for a curved lens to not bend the light, you need it to be taper-corrected—thicker in the middle and thinner toward the edges. Oakley’s patents on this correction have expired. It’s also important how it fits on your face and how it’s put into a frame. The curvature of the wraparound as well as the pantoscopic tilt (the rotation of lens bottom towards the cheeks) when it’s on the face matter, and we build ours to fit a standard head form.

More distortion in the lens causes eye strain over time, and how the eyes are affected depends on the person and on what they’re doing (with the glasses on). Some people notice right away if there is a lot of distortion in the lens, and some people don’t notice it at all.

I just recently came on board here, and I’m making changes across the board on all of our models to improve the optics.”

As for polarization, Oman says that full polarization is a bad idea for cycling glasses because if there is oil or water on the road, you won’t see it. He thinks that new technology in partial polarization can be great for cycling because the rider can still distinguish, water, oil, and dips in the road while reducing much of the glare and hence eye strain. He is working on this with lenses ranging from 85% to 40% polarization.

From KOO:

“The kind of test you are mentioning is included in the test range for conformity that we make for all our products. For your information, we are sharing with you an extract of the test certification results (this document is confidential) that declares our compliance to regulation ISO 12312-1:2013/Amd 1:2015 and ANSI Z80.3-2018 regarding the lens clarity for vertical and horizontal light distortion.

It is mandatory to pass these tests in order to sell sunglasses in Europe, and Worldwide as well. I’m afraid that we are not able to comment on any tests made on lenses of which the quality is unknown (referring to the comparative lenses with which Oakley is doing their tests).

In order to fulfill all the necessary requirements, we rely on ZEISS, as our lens manufacturer, to carry out their quality inspection tests and stringent internal standards. All the sunglasses that have been tested by ZEISS laboratories that have passed the ZEISS Optical Certification are published on their website as ZEISS qualified.

Regarding eye health, our sunglasses’ lenses are tested in order to verify any sight distortion issues.  The spherical and astigmatic power of lenses is tested. The difference value between right and left lens/ or single-lens side is tested as well, to avoid any vision distortion. These tests are conducted using the same machines found in ophthalmology labs. The only valid test required to be compliant with EU/ANSI Regulation is the one made by the Notified Body.”