Home Optics Optics 101: Anti-Reflective Lens Coatings

Optics 101: Anti-Reflective Lens Coatings

Various lenses

Lens coating was discovered by Alexander Smakula, a Carl Zeiss engineer, in the 1930’s. He was credited for developing it, and this completely changed the world of optics.

Pretty much every lens you’ve ever looked through has a lens coating. Be it a camera lens, a rifle scope, a binocular, and a spotting scope. All kinds of optics need to transmit light from one end to the other for the user to see where it is pointed at.

Optics like spotting scopes, use lenses, prisms, and mirrors to transmit light and images to the user. Without the coating, what you would deal with is two distinct problems:

  1. Less light would be transmitted through the optic.
  2. Internal surfaces — the mirrors, lenses, and prisms, would cause light to reflect away from them.

Spotting Scopes & Lens Coating

Lens coating is a simple, often ignored feature in spotting scopes. It gives the user a clearer, brighter picture. Without it, using optics in low light conditions would be near impossible.

Spotting scopes are high powered and feature wide objective lenses. Those two factors make achieving proper clarity difficult and make the basics of optic’s construction very important. One of those basics is high-quality lenses and lens coating.

Lens coating primary job is to prevent reflection and refraction of light. This affects the air to glass, and glass to glass surfaces of a spotting scope.

 

 

Let’s Dive Into the Different Types of Lens Coatings

Spotting scope lens close up

Single Layer AR ( Anti-Reflective ) Coating

Single layer anti-reflective coating is the oldest style of lens coating. As soon as Carl Zeiss introduced the idea and it proved successful, the technology exploded. These days, a single layer AR coating is the standard for almost all optics. It reduces the light lost from reflection by more than half.

Single layer AR coating is designed to be useful with one particular color of light. To match that one color of light, coating thickness needs to be equal to one-quarter of the wavelength. Outside of that one particular wavelength, the coating becomes less effective.

 

Single Lens Coating

Single lens coating, or simple coated lens, is a single layer, thin coating that is applied to one or more of the lens surfaces. This thin layer of transparent film was the first coating method invented by Alexander Smakula. The layer is so thin it’s roughly six-millionths of an inch.

 

Fully Coated

A spotting scope that features fully coated lenses means every lens that is air to glass has a single layer of coating. While this is more efficient for single lens coatings, it’s still far from perfect.

 

Multi-coated

Lens coating comparison
Source: Nikon

Multi-coated lenses have multiple layers of coatings on one or more lens surfaces. They cure the deficiency that comes from the single layer lens coating.

Instead of the coating working only with one color or wavelength of light, it works effectively with a multitude of wavelengths. It is used by most serious optic manufacturers. Multi-coated lenses reduce light lost from reflection to .02%.

 

Fully Multi-coated

Fully multi-coated optics has multiple coatings on every lens surface. They are the standard on high-end optics and reduce light reflection more than any other system.

A full multi-coating does not make poor quality lenses or construction any better. However, it is a good sign of the construction quality of a spotting scope.

 

The Other Side of Lens coating

We’ve established that lens coating improves the overall picture and view you get from a spotting scope. This is obviously one of its most important aspects. However, this isn’t all it does. It also protects the actual lens of the optics.

Tough Coatings

Companies like Leupold and Burris both offer lens coatings that are excellent at transmitting light. They also have the benefit of protecting the lenses from abrasions, scratches, and other external damage.

These sturdy layers are designed to address the dirt and debris that are often whipped around by the wind and the general abuse that outdoor gear receives. A spotting scope and its large objective lenses are big targets for abuse so these coatings can work wonders.

 

Water Resistance

Bushnell Rainguard

Water resistant coatings do not protect the lens from the water. Instead, it makes it possible for the scopes to work when wet.

A spotting scope covered in water drops can be difficult to use and see through. Bushnell Rainguard is probably the most famous coating for water resistance. It essentially allows the spotting scope to ignore the water on the lens, and use it without hesitation.

 

Final Thoughts

When shopping for a spotting scope or any other optic, lens coating is an important factor to consider because a poor lens coating can make the optic useless at certain parts of the day.

Consider your options wisely and when in doubt, a fully multi-coated optic is usually the ideal way to go for a clear picture and a versatile scope.

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Travis Pike

Travis Pike is a former Marine Machine gunner who served with 2nd Bn 2nd Marines for 5 years. He deployed in 2009 to Afghanistan and again in 2011 with the 22nd MEU(SOC) during a record setting 11 months at sea. He’s trained with the Romanian Army, the Spanish Marines, the Emirate Marines and the Afghan National Army. He serves as an NRA certified pistol instructor and teaches concealed carry classes

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