How Do Polarized Lenses Work?
Polarizing Lenses Explained
What are Polarizing Lenses? In sports and other outdoor leisure activities we react to what we see. We see by virtue of the light that enters our eyes. Without good sun wear, brightness and glare will diminish our best efforts. Glare results in a loss of visual performance, which is produced when an object or light source in the field-of-vision is brighter than the amount of light to which the eyes are adapted. Most tinted lenses will provide some absorption to dampen brightness, but only a polarized lens can effectively eliminate blinding glare.
What causes glare?
Light is made up of waves travelling in different directions. Vertical light is useful to the human eye; it helps us see. Horizontal light, however, simply creates glare. Glare is concentrated light reflecting off a horizontal shiny surface, such as a car windscreen, sand, water, snow or asphalt roads. It reduces visibility and can make it uncomfortable, painful and even dangerous to carry on driving, cycling, skiing or just sunbathing.
How do polarized lenses compare to standard tinted sunglasses?
Regular non-polarized sun lenses indiscriminately filter all light whether it is horizontal or vertical. Glare is dampened, but not eliminated. More importantly, by filtering all components of light, visual acuity is diminished. On the other hand polarized lenses allow in the vertical component of light, which is preferred for clear vision, while eliminating the easily scattered and skewed horizontal component of light. Vertically aligned light is preferred because it respects the natural tendency of the visual system to focus on the vertical component of an image.
Why are polarized sunglasses beneficial for water sports?
The glare of the sun on the sea and other water surfaces is highly polarized. Indeed, the glare can be almost completely horizontally polarized, depending on the height of the sun. In addition, all reflections from objects above water are partially polarized. These include clouds and even the sky (the reflected sky gives most of its blue colour to the sea).These are examples of polarization by reflection. Although the light from the sun is not polarized, it can be separated into two polarized components that are reflected and transmitted in different amounts by the surface of the water. More of the horizontal component will be reflected than the vertical component, thus partially polarizing the reflected light. With polarized sunglasses they will stop the glare and make the sea appear more transparent enabling you to see fish and rocks below the surface.
Why are polarized sunglasses beneficial for driving?
Polarized sunglasses help when driving a car by reducing those bright reflections of the sun on the cars ahead. They tend to be horizontally polarized, thus perfect for vertically polarized sunglasses. The reason is that the surfaces that you see on the car in front of you (the back window, the rear door, and even the roof) is slanted towards you, while the sun will be more or less aligned in the vertical plane through both cars. Polarizing lenses will provide higher definition vision for driving, remove dazzling effects and reduce eye fatigue.
What are the advantages of polarized lenses?
A polarized lens offers the following advantages over non-polarized lenses:
- Improves visual comfort
- Improves contrast and visual clarity
- Reduces eyestrain
- Allows for true perception of colors
- Reduces reflections and eliminates glare
When could polarized lenses pose a problem?
For certain sports or activities, polarized lenses are not the best choice. These are as follows:
- Skiing in icy conditions. Patches of ice are easily identifiable as they reflect more light than snow. Wearing polarized lenses will make icy patches more difficult to see.
- Spotting oil or icy patches on the road. For the same reasons above, at eyekit.co we do not recommend using polaroid lenses for riding motorbikes.
- Viewing liquid crystal displays (LCDs) – Polarized lenses can make the liquid crystal displays of certain objects more difficult to read. As most modern motorbike instrument’s and the instrumentation in modern aircraft have LCD displays at eyekit.co we do not recommend their use.
How do I know if my sunglasses are polarized?
Just look through the glasses at the reflection of any object on a window panel. Then, turn the sunglasses around as if they were the hands of a clock facing you. If the intensity of the reflection doesn't change with respect to what you see through the window, they are not polarized.
Another way is to hold them at 90° to another pair labeled as polarized and if the lenses go dark where the lenses overlap, then your sunglasses are polarized too. If there’s no change, your lenses aren’t polarized.
Do polarized sunglasses work better at different times of day?
Yes. Maximum polarization is obtained when the sun is at about 37 degrees from the horizon. If the sun is very low or very high the sunglasses will be of little help in filtering the glare in calm seas. A rule of thumb would be that polarized filters limit the glare from calm waters for a sun altitude between 30 and 60 degrees.
Can I have clear polarizing lenses?
No. Owing to the parallel row alignment of the iodine crystals, if they were clear they would not block light in a specific direction.
Are all polarizing lenses the same?
Not all polarization is equal. Because not all polarized sunglasses block glare as well as they should. A polarizing filter is no guarantee of an effective glare-blocking lens. It depends on the quality of the filter and how the lens has been produced. Cheap polarized sunglasses may only cut out 10% of reflected light, but many people don’t realize there is a difference in filter quality in better made glasses. For example, Julbo Polycarbonate Polarized lenses cut out around 60 – 70% of reflected light, and the NXT Cameleon, Octopus and Polar HD lenses cut out 99% of reflected light.