ANTI-REFLECTIVE COATINGS
Anti-Reflective coatings are also often referred to as AR coatings. In our opinion it is one of the best upgrades anyone can make to a pair of glasses, with some exceptions. The basic principle behind an anti-reflective coating is to reduce the reflection of light off the lens. By reducing glare, you help to improve the efficiency of the lens and how light interacts with it. However, as with all items there are different levels, qualities and applications methods, with better quality applications providing improved optics and therefore improved vision.
AR coatings have been around since the 1930's when the Zeiss optical company first introduced the idea in a commercially viable form (Fun Fact: The original theory was developed back in the late 1800's by Lord Rayleigh, the same gentleman who proved mathematically why the sky is blue). Since than AR coatings have become the standard for all lenses in europe, but to this day only make up a small fraction of the lens purchases in north america. This is because of problems with early version that would often craze, a process by which the coating would crack, peel or separate from the lens.
The difference between quality coated lens and less expensive version can be broken down in to a couple of areas.
1. Front surface only coatings or back surface only vs. front and back surface coatings - By only coating one side of the lens, its obviously less costly to apply, plus there can still be reflections off the uncoated surface. The one application however where a back surface only coating is preferred, is in sunglasses. This is because you want sunlight to be reflected off the front of the lens but you don't want to see the reflection of your own eye.
2. Single layer coatings vs. multi-layer coatings - A single layer coating is easier to apply but must be applied in a slightly thicker coat (like paint, one thick coat can flake off). It also only provides good reflective properties over a very small spectrum of light waves, so reflections can still occur. A multi-layer coating is more costly to apply, but provides good reflective properties over a large spectrum of light waves reducing glare even more. It is also less likely to flack off, as its applied in thinner layers.
3. The addition of a hydrophobic coatings to help repel water and grease - Anyone who has owned a pair of AR coated lenses understands that they can get dirty easily. The manufacturers have known this for years, and have now started incorporating ways to reduce this. These additional processes also help to make the glasses easier to clean.
Why should I buy an AR coating?
1. Reduced surface reflection - This helps to improve the over all cosmetic appeal of the glasses, by allowing others to see your eyes. It draws attention away from the lens and centers it more on the frame, or makes the glasses seem invisible in rimless styles. Reducing surface reflections also helps to reduce ocular fatigue while working on computers, working under fluorescent lights or from ambient light from windows or floor lamps. Additionally, it helps to dramatically reduce night time glare when driving, from headlights, street lights and internal car lighting.
2. Improved light transmission - All smooth surfaces reflect light (eg. reflections of water, snow, etc. ) and all clear materials reflect light internally (This is why you pay big money for well cut diamonds). Anti-reflective coatings help to reduce both of these principles. This means that more light is able to pass through the lens instead of being reflect off or reflected internally. This does 2 things, increases the brightness of the images and improves contrast sensitivity (fine detail vision). Typical uncoated lenses transmit about 90-92% of light, verses well coated lenses which transmit 98-99% of light. It may not seem like a lot, but try rolling down the window in your car and comparing the before and after, or look at your backyard through the patio door window and than open it (most car windows and home windows have no AR coatings). Even this subtle increase in light transmission can make a night and day difference in low light levels. Improved light transmission also makes your vision through glasses seem more natural.
3. Improved Scratch Protection - One interesting property of most AR coatings is that they provide a very hard durable surface to the lens, thus making the lens scratch resistant. Remember, no lens is 100% scratch proof not even glass. So proper care and maintenance is still required when cleaning your new lenses.
