Optics 101: Anti-Reflective Lens Coatings

Various lenses

We live in a time where optics are clearer than they have ever been before. You can see farther and better in low light conditions, allowing you to hit what you’re aiming at. This is due to a few factors including higher quality glass, better construction, and the use of lens coatings. 

Of these 3, the factor most people misunderstand is lens coatings.

Pretty much every lens you’ve ever looked through has a lens coating. Be it a rangefinder, 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 companies really love to toss around phrases like “proprietary fully multi-coated optics”, and “anti-reflective lens coating.”

What do they mean though?   

Today we are going to answer that question for you. We will be discussing what they are, what they do, and how they affect your optic’s choice. Get ready to explore the world of lens coatings! 

 

A Little Lens Coating History 

Carl Zeiss lensOptics that magnify images have been around for hundreds of years. Sea captains and sharpshooters are among the many people throughout history who have benefited from optics. However, they were much different from the lenses of today.   

It is interesting to look back at early optics. If you do, you’ll notice how big they are. With all that size you would think they could see halfway around the world! But alas, they were greatly limited due to a lack of lens coating and low-quality glass. 

In 1930, an engineer at the Carl Zeiss factory discovered a means to cover lenses. This anti-reflective coating revolutionized the industry. During WW2, both sides developed their own coatings and the future of optics was forever changed.   

Since then a variety of new coatings have come into existence. The most important type is anti-reflective, also known as AR coating. AR is still applied to all optics, but the methods used and where it is applied have evolved from the early days.   

Let’s dive deeper into the different types of coatings and talk about what they do, and how they work. 

 

Let’s Dive Into the Different Types of Lens Coatings

Spotting scope lens close up

Anti-Reflective Coatings 

Anti-reflective coatings are the industry standard and a must have on any optic. They reduce reflection and glare, thereby allowing you to see a clearer and brighter picture. Reflection means light loss, and you lose anywhere from 4 to 6 percent per surface.  

When you realize there could easily be 10 surfaces in a modern optic, the amount of light you lose really starts to add up. That reflective light then becomes glare, which reduces the clarity of your picture.  

Glare causes reduced contract, blurriness, and a difficulty seeing fine details. This is why AR is so important to look for in an optic. A single layer of this kind of coating can reduce light loss to 1.5 to 2 percent!  

Multi-Layer Anti-Reflective Coatings 

Single layer coatings were a massive improvement to optics and had their 15 minutes of fame. However, technology has evolved since the early 1900’s. Now multi-layer AR coatings are the standard of quality optics! 

To improve clarity, manufacturers began applying multi-layer anti-reflective coatings over lenses. A single layer coating only works with a specific wavelength of light. Multiple layers allow the lenses to reduce the loss of light over a wider variety of wavelengths.  

High-end optics these days are insanely clear and bright. With a high-quality coating, the loss of light can be reduced down to a fraction of 1 percent. The current high-quality lens coatings can bring a riflescope’s light transmission up to 95%!  

 

Phase-Correction Coatings 

The Carl Zeiss company has always been one to revolutionize the optic’s industry. In fact, they were the ones that created phase-correction coatings for roof prisms in binoculars, spotting scopes, etc.   

Why is phase-correction so important? This coating eliminates an issue known as destructive phase shifts. Destructive phase shifts are the result of light waves reflecting off of opposite surfaces. In fact, they occur due to the natural design of roof prisms.   

 

Water Repellent Coatings  

Bushnell Rainguard

Also known as hydrophobic coating, this feature allows you to see through any rain or moisture that has accumulated on your scope. They resist water, fog, and let you see through your scope without the need to wipe it down first.  

An excellent example of hydrophobic coating use is Bushnell’s Rain Guard HD.  

 

Abrasion-Resistant Coatings  

Anyone who wears glasses knows that lens scratches and abrasions are a major hassle. Due to the outdoor nature of the activities you use your optics in, an abrasion resistant coating just makes sense.  

This type of coating protects both your lenses and the anti-reflective coating on your optic. Usually, these coatings are most often found on higher end tactical optics. An excellent example of an abrasion-resistant coating is the Armortek from Vortex.    

 

Nomenclature to Know  

Coated Optics – The most basic of coatings you can find on an optic, and means one or more surfaces are coated. You won’t really find this on modern optics, outside of some serious reproductions.  

Fully Coated Optics– Fully coated is common on more affordable optics, and means all air to glass surfaces are coated. This will be a single layer of anti-reflection coating. While not terrible for shorter distances, it isn’t great for long-range optics. 

Multi-Coated – This means one or more of the lenses have multiple layers of AR coating. Typically, both the exterior lens surfaces are multi-coated while the interior surfaces have a single layer AR coating.   

 

Lens coating comparison

 

Fully Multi-Coated – This is the big dog of high-end lens coatings. Fully multi-coated means all air to glass surfaces have multi-layer anti-reflective coatings. Since this is the best of lens coatings, it is usually found on the most serious tactical and sporting scopes.

 

Coating Quality 

Vortex monocularBefore we depart, we need to mention that not all coatings are made equal. A fully multi-coated optic that costs $99 is not going to be as clear as a fully multi-coated optic that costs 500 dollars. High-end coatings are like high-end glass in that they are relative to your price range.  

We trust companies like Nikon, Zeiss, Leupold, Vortex, and on the lower end, Bushnell, to provide reliable and functional coatings. There are other great companies out there, but we are only speaking from personal experience.   

We do not doubt that Nightforce, Steiner, and Schmidt and Bender make fantastic optics. However, we do doubt the super tactical optic you find on wish.com for $15 is going to give you a fantastic coating.   

 

Coating Choice 

coated lens
When choosing the coating for you, you will also be factoring in your budget. If you want a fully multi-coated optic, you will pay for it. This type of coating is designed for people who shoot a good distance and want the ability to do so in low light conditions. 

If you are only taking shots out to a few hundred yards at the range, then a multi-coated optic will usually get you there. If you are on a budget or equipping something simple like a rimfire rifle, then fully coated is an option.  

Whatever optic and budget you choose, make sure you are getting your dollars’ worth. Knowing a little about lens coatings is the first step to getting the best value possible out of your purchase. 

 

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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