Why do I need sunglasses?

To protect your eyes from dangerous ultraviolet rays, to reduce glare to a comfortable level, and to improve night vision. We have been is the sunglass business for over 4 decades, we have the experience to help you choose what is best for your particular uses.

What is ultraviolet light? 

Ultraviolet light (UV) is the invisible rays from sunlight that can harm your eyes. Cataract formation has been linked to UV light. UV light is what causes a lot of things to deteriorate, like tires, paint, etc.

What is infrared light?

It's the invisible rays from the sun that are made up mostly of heat waves. Infrared (IR) light has no known harmful affect on humans other than causing discomfort to your eyes, causes contact lenses to “dry out” faster.  IR light can be stopped only by glass sunglass lenses.

Light transmission levels of lenses

VLT = Visible Light Transmission, UV =  the Ultraviolet light and IR = Infrared light. On this website you will see us use these abbreviations to keep the length of copy as short as possible. We use light transmission as a standard measure, this is the amount of light that the lens will allow to pass through. Example; a lens with a VLT of 15% allows that much of the visible light to pass through the lens and reach your eye (it blocks 85% of the light).

If the sunglass provider does not offer visible, infrared and uv transmission levels, you have no way of knowing what you are buying, regardless of price. Price alone is no longer an indication of quality or protection level.

How can I determine what the VLT is on my own?

The levels we provide in these guides are pretty much useless if you have no way of deciding what is dark or light for you. Unfortunately, most of the sunglasses offered (including the most expensive) do not publish their UV, IR or Visible light transmission levels. The only guide we can offer for you to judge on your own is to find a pair of Ray-Ban© sunglasses with the G-15 GreyGreen lenses and look through them, they have had a VLT of 16% for over 40 years. The Randolph Engineering or American Optical Military Issue glasses with the Neutral Grey lenses (Dark grey) also have a 16% VLT.

How do sunglasses help night vision?

If you subject your eyes to intense glare during the day, they will tend to “defend” themselves by trying to adapt to the bright light. This natural built-in defense will persist for several hours after the glare is gone, resulting in much reduced nightvision. Studies have shown that night vision can be reduced by as much as 50% by this exposure. Wearing good sunglasses during the day will improve night vision considerably.

The military has known for decades that troops that are going to go on night operations need to prepare the eyes during the day by keeping them in very low light conditions by wearing dark glasses. This increase their night vision adaptation time to a minimum. If you are a professional driver, pilot or involved in day and night operations, wearing a good pair of sunglasses during daylight hours will help you see a lot better at night.

What is the definition of a good sunglass?

It reduces visible glare to a comfortable level, eliminates most of the ultraviolet and infrared light, produces no distortion, transmits colors with little or no alteration, fits comfortably and is durable.

How do I choose the proper sunglass lens?

First, determine what you are going to use it for most of the time. If driving is your biggest use, then choose one for driving. Don't make the mistake of choosing a sunglass for something that you only occasionally do, like snow skiing or fishing. There are special lenses for all activities, if you can afford more than one sunglass, then choose the best ones for each specific activity. Remember, no one lens can do it all, you may need more than one. We have a "Lens Selection Chart" to help you choose.

How to select sunglass lenses

To provide full, day-long comfort, sunglasses should eliminate all of the problems that glare can present. Lenses of 15% to 30% visible light transmission seem to reduce glare sufficiently. The visible light transmission (VLT) is the amount of light the lens allows to pass through. A 15% transmission is dark, a 30% lens is lighter. Most high quality sunglasses with glass lenses will usually have visible light transmission levels of 15% to 20%. If your eyes are extra sensitive you might require darker tints, we can provide lenses down to as low as 5% VLT, extremely dark

Selecting the darkness of the lenses

General purpose lenses that have VLT levels of 15% to 20% work best for people with "normal" light sessitivity. If you are going to spend a lot of time fishing, snow skiing or boating, you might get a darker lens, say around 8% to 12%.

If you have extra sensitive eyes, you could go down to 8%, or even less, but we normally don't recommend lenses darker than 8% unless you have a sensitivity problem. Some people with blue eyes may have a higher sensitivity and require the darker tints.

As you age, your eyes gradually lose their “light gathering ability”, especially after age of 50 or so, therefore you don't need sunglasses as dark, you can move up to the lighter lenses that have a VLT of 25% or even lighter.

Selecting a lens with the correct VLT for you is the first step, next and also as important is selecting lenses that block ultraviolet (UV) light. Since UV light is one cause of cataracts, the lenses should block most of the UV. The UV light transmittance should be less than 10%. The other rays to consider is IR (infrared)—mostly heat waves, it is important to block IR if you wear contact lenses, or spend a lot of time in direct sunlight. Heat waves cause the eyes to “dry out”, thereby causing "scratchy eyes" and adding to discomfort.

Don't get lenses that are too dark. You can become addicted to dark lenses, and they can be dangerous when driving if you go from a sunshine area to a tunnel or heavily shaded area, you will be blinded temporarily if the lenses are too dark.

Don’t judge the density or darkness of the lenses for the first minute or two when you walk from inside a building to outside. The difference in light intensity is like 1000 to 1, and no lens will compensate for that much difference, your eyes will adapt after a minute or two.

Traffic light and color recognition is also important. Some cheap plastic lenses can severely distort colors. If you stick to Dark Grey, G-15, Natural Green or Kontraster™ lenses glass, you won't have a problem with color distortion. If you have an occupation that requires precise color identification, use the Dark Grey lenses, they are the most neutral.

Read through our guide for specific recommendations on lenses for various uses.

How to choose a frame

Choosing a frame (for other than just looks) involves answering a couple of questions. First, are you “hard” on glasses? If you are, you might think about choosing nylon or Titanium memory-metal frames, they are the most durable and will take a lot of abuse. If you take good care of glasses, you can choose any frame material you want. The least durable frames are the so-called “rimless” frames, since the "frame" is the lenses themselves‑they tend to be very flimsy and will take no abuse at all.

Frame nomenclature: There are 2 main parts to frames, the frame front (part that the lenses go in) and the temples.

Skull Temples are usually measured from the point where they attach to the frame to the very tip.

Frame sizing: We measure frames in 2 ways, the old traditional way by measuring the width of one lens (called the lens size), and another way by measuring the overall width of the entire frame.

Have you had problems in the past with metal frames turning green on you? Most frames are made of a nickel alloy, nickel is very strong and durable, but, if you have body chemistry that causes metals to turn green you might choose Titanium or Stainless Steel frames. Both Titanium and Stainless steel are usually much lighter than frames made from other metals, and they won't turn green when in contact with your body. Plastic frames are still preferred by a lot of people, their only problem is that they are much harder to adjust to fit your face, and somewhat fragile.

Frame fit is most important. If the frame can't be adjusted to fit your face, they will be uncomfortable to wear. Choose metal frames with nosepads that have adjustable arms (most good quality opthalmic frames have temples and nose pad arms that can be bent to fit your face), that way you can bend them to fit your nose and face. All the opthalmic type metal frames that we sell can be adjusted.

The human head is distorted. New frames are normally very "square" mechanically. They will rarely fit correctly.

1. Most people have one ear lower than the other.

2. The ears are rarely the same distance from the nose.

3. The ears differ in their verticle position from person to person.

4. The eyes are not exactly on the same plane.

5. The nose is not quite centered between the eyes.

6. Noses come in a lot of different widths and shapes. 

7. Cheekbones come in a variety of positions and sizes.

All of this results in frames that sits crooked on your face. So when you first put a nice "square frame" on your face, chances are real good that it won't fit right.

Temple adjustment: The temples can be adjusted up and down individually to straighten the frame horizontally on your face, this compensates for ears that are not level. You can bend the temples up or down to correct the horizontal position (nylon frames and many plastic frames can’t be bent to make this adjustment).

If temples on metal frames are too long, you can bend the tips down more to make them shorter to fit better, this adjustment will also keep the frames from sliding down your nose.

If the temples don't go down behind your ears where they belong, you can take some of the bend out to make them longer, or, you might need a different size temple.

Frame "Tilt" adjustment: If the bottom of the lenses are too far away or too close to the bottom of your face, you can bend both temples up and down to tilt the frame correctly on your face.

Nose Pad Arm adjustment: The nose pads can be adjusted to allow for crooked or offset noses, wide or narrow noses, and to position the frame in the correct position on your nose vertically. 

Frame size is important to everyone, but especially people who have prescription lenses. The smaller the frame size, the thinner and lighter the lenses will be. If you choose glass lenses, smaller frames will produce lighter lenses and add to your comfort. Rimless frames have gotten really popular lately, they look really good, but you must consider the weakness of these glasses. In a rimless frame, the lenses are the frame, and lenses are not real strong, so if you are not careful, you can expect some frame/lens problems with them.

Which sunglass lens is best

There are many lenses available for both general and specific uses. We are in the business of selling top quality, effective sunglasses. If you shop at local stores, and the merchandise is not marked with the visible light transmission (VLT) and filter characteristics of the lenses (amount of UV and IR filtered), you have no way of knowing what you are buying. We publish as much information as we can about all of our lenses and frames. Price is no longer an indication of quality, and has not been for quite a few years. With all of the hype and marketing of so called “Brand” names, the consumer has almost no resource to check the quality of what they are buying. There are so many designer “name brands” now days, some named after dead people, animals, ficticious designers, children, things, cars, etc. that the consumer is left trying to decide on “brand”, when he should be taking a hard look at the merchandise itself to see if there is any value there. The suggestions here are based on our 43 years experience in this business.

Glass or Plastic lenses?

The first decision to make is the lens material.We'll give you all the pros and cons of all the lens materials.

GLASS lenses

Advantage: Glass lenses are optically superior and have several advantages over plastic lenses, the most important ones being higher scratch resistance, clearer vision and better filtration offered by the glass sunglass lenses.

Advantage: Glass is much clearer that plastic (clear glass lenses have a VLT of about 93%, the VLT of plastic is about 85% at best). The better filtration comes from the fact that colored glass stops both infrared (IR)and ultraviolet (UV) light, and is more consistant in density and color. Objects always appear much sharper looking through glass sun lenses than plastic sunlenses.

Advantage: Glass lenses generally outlast several pair of plastic lenses because of superior scratch resistance. Glass lenses are also more chemical resistant than plastic, will not scratch as easy from improper cleaning.

Disadvantage: The downside to glass lenses is that they are heavier than plastic, and even though they are heat treated and very impact-resistant, they are not as impact-resistant as polycarbonate plastic lenses.

Disadvantage: Another problem with colored glass lenses is that for prescription use the uneven thickness of the prescription will cause the lenses to be thinner or thicker in areas, thus causing lighter and darker areas across the lenses. If your prescription is over 2.50 (under the sphere column) you might consider going to plastic.

Examples of Glass prescription lenses:

 

This illustration above is a minus (-) 2.00 (sphere)  plastic lens that has been tinted, notice the density is even across the lens. The color density across the lens will alway be even in plastic lenses, regardless of the prescription thickness.

 

 

This illustration is a minus (-) 2.50 (sphere) colored glass lens, so it is thicker on the edges and thinner at the center, so you can see that the edges are darker than the center.

The illustration above is a plus (+) 2.50 (sphere) colored glass lens, this lens is thicker at the center and thinner at the edges, so it is darker in the center and lighter on the edges.

The illustration above is a picture of a colored glass plus (+) 2.50 sphere with a trifocal, the center is darker than the edges and the bifocal is much lighter than the rest of the lens. 

The glass lens above is a Serengeti Top-Gradient density Driver lens, note the top is darker than the rest of the lens.

Glass lenses are available in regular crown glass, and thin high-index glass. Most of the glass lenses we offer are only available in crown glass, if your prescription is thick, and you want glass lenses, there is another material out there that produces thinner glass lenses. We'll just call it thin glass without going through technical descriptions. If you don't see it listed on the prescription glass page, call for availibility.

Color coating glass lenses: Colored Glass is not always available in many lens designs, and if your prescription is on the thick side, colored glass lenses will have an uneven density as explained above. If you like the clarity and scratch resistance of glass, here is an option.

You can have any clear glass lens color coated. The color is applied to the back side of the lens where it is protected from scratching. They look just like their solid colored glass cousins, except the density of the lens is nice and even across the entire lens (like the plastic lens shown above), regardless of how thick the lenses are. Some lenses (Such as the Copper Driver lenses) can only be had with color coatings, as there is no colored copper glass available. Also, if you need a really dark lens, you can have color coating put on the back of colored lenses and bring the VLT down to about 8% (twice as dark as normal colored lenses). Although color-coatings are somewhat expensive, they are usefull and even necessary in a lot of cases.

The single big advantage that plastic lenses have (CR-39) is they can be tinted to any density from clear to opaque, and anything in between, so they offer a wider selection of “darkness” as well as the availability of Top-gradient density tints.

 

Advantage: They produce a nice even tint across the entire lens, they don't have light and dark areas like colored glass. Plastic lenses shrink with age, this is not a problem on most ophthalmic frames, but if the frame is very thin (such as Ray-Ban metals) the lenses can shrink enough to fall out of the frame.

Disadvantage: Tinted plastic lenses produce a phenomenon we call “red lenses”. When you hold your tinted lenses up to outside light, they appear whatever color they're tinted, if you hold them up to an incandescent lamp, they will appear red. Or, if  you look at yourself in a mirror under incandescent light, the lenses will also appear red. Without going through a lengthy explanation, suffice to say that you are looking at a filter, through a filter. This is normal for plastic lenses.

Disadvantage: Lower visual acuity; because glass lenses start out with a higher light transmission (about 97%), they are clearer than plastic lenses that generally have a light transmission of around 84% or less.

Disadvantage: Tinted plastic will lose some of their color after a while, they tend to get lighter, some turn to a kind of magenta color. Colored glass lenses keep their color forever.

The 3 kinds of plastic lenses

CR-39 plastic is the most popular lens material used for prescription lenses. It's light, easy to work with, can be tinted to any density, and is more scratch resistant than polycarbonate plastic.

Polycarbonate plastic is the material used on almost all cheap over-the-counter plastic sunglasses, and some very expensive one also, it has the highest impact-resistance and is used most often used for prescription safety lenses. It is soft so it scratches easy, and it can only be tinted to a medium density (about 35% LT) only, no darker. This material is used in all rimless frames. One advantage of Polycarbonate plastic is that it is lighter and a little thinner than CR-39 for the same prescription.

Thin Plastic (high index) is high-density plastic that has a higher refractive index than regular CR-39. This means that lenses will be thinner using this material. If your prescription is over + or - 5.00 (under the sphere column), and you are using a large diameter frame, like a 60 eye size, using this material will make the lenses thinner and lighter. Most of today's frames are so small that there is not much of an advantage to this material, if you use smaller frames like eye size 48mm or so, you won't notice them being much thinner until you reach prescriptions of + or - 6.00 or more.

Which lens is best for specific uses

If you don't have time to read this guide, see our Sunglass Selection chart. Our recommendations are based on glass lenses. Here is a list of the most common uses for sunglasses.

      Dark Grey              G-15 GreyGreen             Kontraster             Natural Green

For GENERAL PURPOSE the Dark Grey, G-15, Kontraster™ and the Natural Green glass are all good. The all 4 of these have light transmission of around 16 to 17%, they are all dark enough to handle daily use under normal conditions. They all work well for general purpose use. If you need to eliminate reflected glare (such as glare coming off the water, the highway, trees, etc.) the polarized lenses work better.

For DRIVING, all of the general purpose lenses work well. Polarized lenses eliminate some of the reflected glare off the highway, trees, water, the hood and windshield that normal sunglass lenses only reduce. If price is not important, the polarized lenses work well for driving. However, the non-polarized Dark Grey, G-15, Kontraster™, Copper Driver and the Natural Green glass do what a sunglass is supposed to do, they dim the light and protect you from IR and UV rays. The disadvantage of polarized lenses is that they "black-out" LCD displays that are found on a lot of speedometers, cell phones, radios, etc.

For FLYING the choice of our customers is the Kontraster™ glass (VLT=17%). It not only reduces glare, and blocks UV and IR light, but increases contrast. By filtering out more blue light it makes things look more vivid. Pilots like it because it reduces the effect of haze and smoke in the atmosphere to make it easier to spot other airplanes and to see ground check points easier. A second choice would be the Dark Grey or G-15 (LT=16%) glass, they do what a sunglass is supposed to do, they dim the light and protect you from UV and IR rays. A third choice is the Natural Green (VLT=16%), it is the best sun filter, blocks almost all of the infrared and most of the ultraviolet light.

A note to pilots about polarized lenses. They should not be worn while flying. In fact, you can't even see through the windshield on most jets while wearing them because the windshields are laminated and cause severe color distortion. On the lighter airplanes you could wear them, but because the axis of the sunglasses are oriented at 90 degrees, as you bank the aircraft it causes the “world to change”, reflectiions off of body's of water will come and go. Also, since they reduce the effects of reflected glare, it makes seeing other air traffic more difficult. Also, polarized lenses make LCD displays (such as used on GPS units, radios and some gages), "black out", if you tile you head at about 90 degrees you can see them again. Many pilots like the Serengeti Drivers, you can now have them in prescriptions, either from Serengeti or from us as the  "Copper Driver" lenses.

For BOATING and FISHING the darker polarized lenses work best. The Dark Grey polarized (VLT=12%) is good for general purpose use on the water, the Kontraster™ polarized (VLT=16%) is better for fishing or any use where you are looking below the surface of the water to identify fish movement or other objects. The Kontraster™ polarized will make the bottom features underwater stand out better so you can see fish, rocks or grass easier. Also, remember, the Kontraster™ reduces the effect of haze, so you can spot buoys and landmarks easier. The downside to polarized lenses on boats is it makes it very difficult to read instruments that have LCD displays, the manufacturers put polarizers on the faces of these instrument that are aligned 90 degrees from the polarized sunglass lenses, so you'll have to tilt your head to read the LCD instruments. 

For SKIING the Dark Grey, G-15 (VLT=16%), Kontraster™ (LT=17%) and Rose Smoke lenses are the top choices. Don’t use polarized lenses, by eliminating reflected glare they mask ice patches on the slopes. On dull overcast days many skiers wear yellow lenses to increase contrast. At high altitudes the amount of UV light increases dramatically, whatever lens you choose, make sure it gets rid of most of the UV light. If safety is important to you, use polycarbonate plastic lenses, although they scratch easier, they are the more impact-resistant. The CR-39 plastic lenses can be tinted to any density from clear to opaque, so if you want extra dark lenses for skiing we can reduce the visible VLT to anything you want.

HUNTING and SHOOTING require protection first, which means that the lens size should cover your eyes well, and secondly, they should sharpen your vision as much as they can. If you are shooting or hunting under low light conditions, the yellow or amber lenses work best. They increase contrast to sharpen things up. If you are hunting in bright conditions, lenses with a lot of yellow or amber work best, like the Kontraster™. If you wear prescription glasses we can tint CR-39 lenses to any density you want to cover any light condition. Some hunters prefer the Natural Green glass, because they are not as dark as the Dark Grey or Kontraster™ glass lenses they allow you to wear them under a greater variety of lighting conditions while still offering the maximum UV and IR protection. A lot of folks use the Changeable Grey lenses because they will automatically darken and lighten as light conditions charge. Probably one of the most popular hunting lens is the Autumn Gold (AmberMatic), they go from light yellow under poor light, to dark brown under bright conditions, and if it is cold and bright they will turn grey. The down side to Autumn Gold lenses is that they have become very expensive. Some people also like the Serengeti Driver lenses (our Copper Driver).

Lately there has been some interest in Teal colored lenses for sporting clays, Teal is available in CR-39 plastic lenses as a tint.

For GOLF and TENNIS keeping track of the ball can best be accomplished with the Kontraster™ (LT=17%). Since it filters more blue light, it makes the balls stand out from both the blue sky and green background. Many people like the Natural Green (LT=30%), it can also be used, they are not as dark as the Kontraster™, but some people prefer the lighter tint because it makes it easier to see golf ball as they drift off into shaded areas Lately there has been some interest in Teal colored lenses for both of these sports, Teal is available in CR-39 plastic lenses as a tint.

For BACKPACKING and CYCLING any of the general purpose lenses will work fine, except for cycling, if you wear a full face shield do not use polarized lenses, as the face shield stress marks will show up and interfere with your vision. Some cyclist like the Changeable Grey lenses that self adjust to changing light conditions so they can use only one pair of glasses all day.  The changeable lenses work well for backpackers as well, except if you are going to be at very high altitudes where the changeable lenses do not filter UV light as well as the general purpose lenses.

If you wear CONTACT LENSES we've found that lenses that stop both UV and IR (infrared) light are the most comfortable. The IR light causes your contacts to “heat up” and dry out faster. Any of the general purpose lenses made of glass will work.

COMPUTER CRT screens and FLOURESCENT lights can cause a low glare condition that is bothersome. One of the most effective ways of cutting this glare from your prescription lenses is to apply an anti-relfection coating (AR coating) to your lenses. This will eliminate the glare on your lenses. If the intensity of the light bothers you also, adding a very light “Softlight” tint will reduce the intensity of the light about 20% to a more comfortable level. So a light color tint and an AR coating are the best combo for this glare.

 

NIGHT DRIVING glare bothers a lot of people. One of the best preventative measures for improving your night driving vision is to wear good sunglasses during the day, especially during the last few hours of daylight. This will make your dark adaptation time shorter and improve your night vision considerably. If you do this and you still have a problem with night driving glare, you might try putting an anti-reflection coating (AR coating) on your clear lenses, and add a Softlight or light yellow tint to cut the glare down. You can't darken glasses much for night time use, but the Softlight (VLT 82%) or yellow lenses have a high VLT of around 75% or so, so it shouldn't interfere with your night vision. Zeiss makes a “Gold AR coating” especially designed for night use. The 

broadband AR coating also works well at night. The ultimate night driving lens is the Softlight or light yellow with a Zeiss Gold coating.

Medical problems can also require certain lenses. If your doctor prescribed certain lenses for you, call us on our toll-free number to find out if we can help you. There are all kinds of lenses out there to help you with certain eye diseases.

So-called “old eyes” can make seeing under poor light difficult. As we age our eyes “wear out”, they require much more light to see well. If you are having difficulty reading at night, try putting brighter bulbs in your reading lamp, if you had 60 watt bulbs, try 100 watt bulbs. Correct reading lenses will also help.

 

GLASS LENS Descriptions 

      Dark Grey              G-15 GreyGreen             Kontraster             Natural Green

 

DARK GREY or G-15 glass lenses have identical characteristics.  Dark Grey (like the Military issue) lenses are a blueish/grey color, the G-15 is Greyish/green in color (like the Ray-Ban). They both do the same thing, they lower the glare intensity to a comfortable level, provide UV and IR protection, and have a VLT of about 16%.  Available in non-prescription and prescription lenses. Used for general purpose use. The Dark Grey will not alter colors that you see.

KONTRASTER™ glass lenses are amber/brown in color, about the same color as an amber/brown beer bottle. VLT is about 17%. so they can be used for general purposes. With the high amber content of the lens it filters light a little differently than the other lenses. It filters more blue light, thereby increasing the contrast of what you see. Since it filters more blue light, things appear clearer, improves depth perception, and reduces the effects of haze and smoke and light fog (which is made up of scattered blue light).  

Pilots like this lens because it makes checkpoints easier to see, and spotting other air traffic is easier. Fishermen like this lens because it makes it easier to spot buoys and other water markers. 

People who live in climates that produce a lot of overcast but bright days like it because it “brightens up” your world, is less depressing than wearing grey lenses on those grey days. Skiers like it because it not only cuts through light fog and haze, but produces enough contrast to see moguls easier. If you are in to almost any kind of outdoor activity, you will find this lens to be the best choice by far. Although it appears to be lighter in tint than the Dark Grey or G-15, the VLT is only 1% more.

NATURAL GREEN glass has a light transmission of 16%, stops all of the UV and IR light, is the only lens capable of doing that. This is still a favorite lens for most of the world.

SOFTLIGHT glass lenses have a light rose color, a very high VLT of about 82%, you can hardly tell they are tinted, appear almost clear. But, they have just enough tint to reduce the glare inside from overhead lighting and even make good computer tints. Available in prescriptions or non-prescriptions. Make an excellent night driving glass, especially with an AR (anti-reflection) coating. In glass they are available on in this light rose color, in plastic we can tint them light blue, yellow, green etc., almost any color you want. Softlight is considered a "light tint".

 

POLARIZED GLASS lenses eliminate reflected glare that other lenses on reduce. Because these lenses have special qualities we have a whole section in this guide devoted to them, click on Polarized Lenses.

Copper Driver lenses start out as clear glass lenses, a color coating and anti-reflection coating are added to make them look just like the Serengeti lenses. If you put this solid coating on clear glass lenses the VLT across the entire lens will be 31% (medium tint). If you request the Top-Gradient coating the top VLT will be 10%, the center 21% and the bottom 30%. This coating can be put on any clear glass lens, single-vision, bifocals, progressives, trifocals, etc. Coating is also available on Changeable Glass lenses, see the section on Changeable glass lenses for description.

MIRRORED GLASS LENSES start out as Dark Grey, G-15 Kontraster, etc., and a mirror is then applied to the front surface. This is one way of reducing the overall VLT of glass lenses. Example; you put a full mirror on a Kontraster™ glass lens and it will bring the VLT from 17% down to about 5 to 7%.  We can not specify the exact VLT because of the way the coatings are applied in batches, so the above figures are about as close as we can estimate. The downside to mirrored lenses is that they can cause severe sunburns on your nose and face due to them reflecting the sunlight, doubles the amount of UV on your nose and the front of your face.

 

CHANGEABLE  lenses

 

Changeable lenses such as the Changeable Grey, Photogrey Thin & Dark, Serengeti Driver, Transitions and the AmberMatic (Autumn Gold) get darker and lighter depending on how much ultraviolet light is striking them. In the plastic version they are called “Transitions™” (this is a trademark name) or the Corning Sunsensor. We will refer to them all as changeable lenses, they all have very similar characterics.

 

How changeable lenses work

 

To darken, they must have ultraviolet light striking them directly. They won't darken inside a car or sitting behind windows, they must be exposed directly to sunlight. When the source of sunlight/ultraviolet light is removed, they go back to their light state. Some will darken as much as to 13% in cold bright conditions, and lighten to nearly clear at 86% in the dark.

 

Several things affect the darkening/lightening process:

 

1. The most important condition that affects lightening and darkening is ultraviolet light, the lenses must have uv light to darken. They must me in direct sunlight, they will not darken in a car or even behind a closed window in direct sunlight.

2.  The length of time they are exposed to uv light will determine how dark they get, they usually reach around 50% of their darkness after a minute or two, then will continue to darken for about 10 minutes. 

3.  The temperature of the lenses have a dramatic affect on the darkness, they darken a lot in very cold weather, they don't darken very much in hot weather. Not a good choice for use in the South where temperatures are in the 90's during the summer. The work better at temperatures in the 60 degree and below range.

4.  The thickness of the lens also affects how fast glass lenses darken/lighten, and how much they change. Thicker glass lenses get darker than thin ones and do not lighten as much. Plastic changeable lenses such as the Transitions™ or Sunsensors™ are not affected by lens thickness since the changeable material is a thin coating on the front of the lenses.

5.  The glass lenses have a built in memory, that is, when you first get them they will be slow to change, as you wear them more and more they will change a little quicker. If you put them in a drawer for a period of time they will revert back to the “new” condition  and you'll have to start the process all over. The plastic changeable lenses change faster and are less affected by memory.

We never recommend changeable lenses to people who have a need for serious sunglasses. They perform poorly in hot weather, a little better in cold weather.

 

Changeable lens availability

CHANGEABLE GREY glass will lighten to about 85% inside (almost clear), and darken to about 25% outside (subject to the 5 conditions listed earlier). Expect them to not get this dark in the summer time, the maximum darkness in the summertime will be more like 35% or so. Can be worn indoors or at night, act somewhat like a Softlight tint indoors, and a medium tint sunglass outdoors. Available in non-prescription and prescription lenses. 

PHOTOGREY THIN & LIGHT is also a changeable grey lens but has a wider span, inside they lighten to about 85% inside. Outside in direct sunlight in cool weather they darken to as low as 17%.  In the summer you can expect them to get down to about 25% (medium dark). The lenses are 30% thinner and lighter than the regular changeable grey glass.  Available in prescription lenses only.

AUTUMN GOLD (AmberMatic™) glass lenses are yellow in color in their light condition (about 85% VLT), and will turn amber/brown as they darken to about 25% to 30% VLT. If the conditions are cold, like around freezing, they will turn Grey at about 22% VLT. Available in non-prescription, single-vision and BF-28 bifocals. Used by hunters as an all weather lens.

 

SERENGETI DRIVER solid and top-gradient lenses are copper-colored changeable lenses that start out in their light condition a medium/dark sunglass density (VLT about 24%), and out in direct sunlight will darken to about 12% VLT in cold weather and bright sunlight. Since they start out dark at 24%, they are not suitable for indoor use. They do make a good sunglass in direct sunlight, subject to the 5 conditions for changeable lenses listed earlier. Available only in Serengeti frames. We can get them for you in single-vision prescription or progressive lenses, however, it takes from 3 to 6 weeks and the cost for the complete package (new frame and lenses from their current catalog) is $400 for single-vision, or $600 for progressives. You can choose any frame in their current catalog, they will not put prescription lenses in your frame.

COPPER DRIVER CHANGEABLE glass lenses start out as Changeable Brown glass lenses, a color coating and an anti-reflection coating are added to make them look and operate like the Serengeti™ lenses.

If you put the solid color coating on Changeable Brown glass lenses the VLT across the entire lens will be 24% (medium)  in its’ light condition, and 10% (very dark) in its’ dark condition. A good general purpose sunglass lens.

If you put the Top-Gradient color coating on a Changeable Brown lens, in its’ light condition the VLT will be 8% near the top of the lens (very dark), the center will be about 16% (normal darkness) and the bottom will be 24% (medium). When the lens darkens to it's darkest state, the top will be 6% (extremely dark), the center will be 10% (very dark), and the bottom of the lens will be 20% (also  dark). The Top-Gradient version is for people with extreme light sensitivity. Inside a car this lens will have a VLT about 16% in its’ light condition, only in direct sunlight will it ever reach it’s darkest state.

CHANGEABLE PLASTIC lenses are sold as Transitions or Sunsensors. The are available in Changeable Grey (all the same characteristics as the Changeable Grey glass lenses described earlier, except they change a litle faster). We use either Corning or Transitions Grey  lenses, your choice. They are lighter in weight than the glass changeables, change from dark to light a little faster faster, cost quite a bit more, are available in prescription lenses only. In their light condition they have a VLT or about 70%, in their dark condition they will get down to about 17% (takes about 2 minutes to darken and about 5 minutes to lighten).

 

Plastic tinted lenses

 

Plastic lenses offer the same colors and performance as the glass except that they do not filter much IR light. The nice thing about plastic lenses is that they can be tinted to any density (VLT) you want from clear to nearly opaque, and if the color or density is not right for you, we can remove some of the color to make them lighter or add color to make them darker.

 

GRADIENT DENSITY plastic lenses are really popular because we can tint the lenses darker at the top to filter out more sunlight coming for high angles, make them lighter in the center for normal use, and the bottom can be lighter so you can see the speedometer or read maps easier. They are very flexible as far as density goes, we can make them just about any density you want (in addition to the ones published as dark, medium or light top-gradients). Available in non-prescription and prescriptions lenses.

YELLOW lenses are very lightly tinted lenses used to increase contrast. VLT is usually 70% or so. They are not sunlenses, although they do stop the UV light, the VLT is too high for use as a sunlens. Also used for night driving to reduce headlight glare. Available in non-prescription and prescriptions lenses.

 

SOFTLIGHT plastic lenses have the same characteristics as the glass ones, except we can increase or decrease the VLT of the lenses to suit your use. We normally tint these to 80% VLT (almost clear), but can also make them darker if your are more sensitive to light. The glass Softlight is a very light rose tint, when you order Softlight in plastic CR-39 we can also use light grey, or green, or yellow or any other color to achieve the same results. Rose color is normally used. Available in non-prescription and prescriptions lenses.

TEAL colored lenses are relatively new, used by golfers, sporting clay shooters and some other outdoor sports. We have not found other really good uses for these lenses yet, are continuing to test them.

COPPER DRIVER colored plastic lenses are the same color as the Serengeti Drivers, are available in almost any density (darkness) you want, available in top-gradient or solid tints.

VERMILION colored lenses are red in color, used by shotgun shooters for various events.

 

POLARIZING LENSES

 

What is a Polarizing lens, how is it made? The illustration below shows a cut away drawing of the 3 piece laminated polarizing lens, The outside and inside of the lens is glass or plastic, the polarizing material itself (which is a very thin “Saran Wrap” like tinted plastic) is sandwiched in between the rigid front and back lenses.

 

 

 

So all of the color and filtration qualities of the lens is in the thin plastic material, the glass or plastic outer lenses are clear. This is what makes good polarizing lenses so expensive, it is like buying 3 lenses.

 

What is the  main advantages of polarized lenses?

Polarizing lenses eliminate some reflected glare that other non-polarized  lenses only reduce. The two key words here is eliminate and reflected. 

If you defined a polarizing lens you could say that it eliminates 100% of the reflected glare coming off a flat horizontal surface at an angle of 52 degrees.  The polarizing action diminishes as the angle of the reflected glare decreases or increases from 52 degrees. This means that if you are standing at the edge of a swimming pool looking down at the water, you will be able to see under water glare- free at an angle of 52 degrees, as you look farther out into the pool you will begin to see glare, the further you look the more reflected glare you will see until the polarizer becomes ineffective.

 

Advantages of polarizing lenses:

1. Eliminates some of the reflected glare coming off the dashboard of your car.

2. Eliminates some of the glare reflected off the inside of the windshield.

3. Eliminates some of the reflected glare from the surface of the road.

4. Eliminates some of the reflected glare coming off the windows of other cars.

5. Eliminates some of the reflected glare coming off trees, leaves and grass.

6. Eliminates some of the reflected glare coming off the surface of the water.

7. Eliminates some of the reflected glare coming from haze.

Disadvantage of polarizing lenses:

1. For driving or skiing they mask ice patches by eliminating the surface glare used to identify ice on flat surfaces.

2. For flying they cannot be used in airplanes with thick laminated windshields, like on large airplanes, you can’t see through the windshield because of the stress caused by the laminations on thick glass.

3. For flying it masks the reflections coming off other air traffic, making it harder to spot other airplanes. Will also mask LCD displays like GPS receivers, etc., making them impossible to read.

4. For motorcycle riding or anytime you wear a helmet with a face shield, it shows the stress in the curved plastic shields and causes you to see blue spots on the shield.

5. For boating, while the polarizer works well for eliminating reflected glare off the water, it will mask LCD displays found on marine instruments, making them hard to read unless you tilt your head sideways.

6. Glass polarized lenses can not be tempered and are not a hard as regular glass lenses, so they are easy to break.

 

Don’t forget about what makes a good sunglass lens, it’s ability to reduce glare to a comfortable level, and eliminate UV and IR light. The polarizer goes one step forward by eliminating some of the reflected glare while reducing the direct glare, but it goes one step backward by not eliminating as much IR light. 

So even though it allows you to see underwater if the water is clear, it does not eliminate the IR rays that add to day-long discomfort caused by excessive heat reaching your eye. The comfort of unpolarized solid colored glass sunlens (such as the Dark Grey, American Grey (G-15), Kontraster™ and Natural Green) stops IR light and let’s you see the LCD instruments on your boat, and provides day-long comfort that polarized or plastic lenses can not achieve.

 

Question: I noticed that you keep saying ‘some’ reflected glare, doesn't the polarizing lens eliminate all the reflected glare?

Answer: No, polarizing lenses only eliminate all of the reflected glare reaching your eyes from an angle of about 52 degrees. As the angle of the reflected glare decreases or increases—the amount of reflected glare that is eliminated is reduced. 

 To put it simply, if you were standing in front of a building (like the top illustration shows) with a polarized lens, you would see the reflections. In the lower picture with polarized lens, most of the reflection is gone and you can see through the window. Most of the glare close to you is eliminated, but as you look farther away, you still see some surface glare, that’s because polarizing lenses are only 100% effective at eliminating the glare being reflected from the surface at the 52 degree angle, as the angle of reflected glare keeps increasing until somewhere around 80 degrees it ceases to eliminate the reflected glare. 

Question: Glass polarized lenses are too expensive, what protection will I lose by buying the Dark Gray, G-15, Natural Green or Kontraster® lenses instead? 

Answer: None. If you look at the lens transmission chart you'll see that non-polarized glass lenses are superior to polarized glass, they block the UV as well or better, they give you IR (infrared protection) which the polarizing lenses do not, they have a higher clarity than polarized lenses, and the impact-resistance is much greater because glass polarized lenses can't be made impact-resistant, therefore the are much more fragile. The only thing non-polarized glass lens won't do is eliminate some of the reflected glare. Clearly, the glass non-polarized lenses are superior light filters.

 

Polarized lens availability

 GLASS polarized lenses are more scratch-resistant than plastic ones, they are available in two or three colors, the Dark Grey (which is usually an American Grey (G-15) which has some green in it), and the Kontraster™ (amber-brown color). The reason the Dark Grey lenses have a green tint added is to keep the lenses from turning a magenta color as they age. The polarizer in all polarized lenses use a saran-wrap like plastic sandwiched between two pieces of clear glass as the filter, this is where all the color and filtration takes place, the glass is used to hold the polarizer rigidly in place and protect it. Glass polarized lenses are available in prescriptions and non-prescriptions. Glass polarized lenses are not impact-resistant like our other glass lenses, to temper lenses and make them impact-resistant you must heat the lenses to 1200 degrees, this would melt the plastic polarizer sandwiched between the two glass lenses. So if you are going to use the polarized lenses where there is any danger of flying objects or other hazards striking the lenses, you might consider the CR-39 or Polycarbonate plastic lenses, or just use non-polarized impact-resistant glass lenses.
 

PLASTIC polarizing lenses (CR-39 or Polycarbonate) are lighter and more impact-resistant than glass. Non-prescription ophthalmic plastic polarizing lenses are 2.2mm thick (cheap plastic polarizing lenses are less that 1mm thick made of easily scratched acrylic plastic).  

The CR-39 plastic polarizing lenses offer excellent optical quality, they have a fairly hard surface to resist scratching, lightweight, and are more impact-resistant than glass polarizing lenses. They are available in Dark Grey, American Grey/green (g-15) or Kontraster™ colors, in both non-prescription or prescription.

Polycarbonate polarizing lenses are the most impact-resistant, preferred by people in fast moving outdoor sports such as fishing, playing ball, etc. The downside is that they scratch easily, so you will need to clean them carefully.