How Binocular Lens Coatings Work

If you hang around enough hunters or spend time glassing with other folks, you’re bound to end up talking about optics. When the topic of “good” optics comes up, one term that’s thrown around is lens coatings. Along with light transmission and a slew of other terms, there can be some confusion when it comes to the factors that truly affect the performance of a binocular.

There are MANY different types of optical coatings, especially when it comes to long-range hunting units. Some that may sound familiar are Swarovski’s SWAROBRIGHT, Leupold’s Twilight Max, and the T* coating from Zeiss. These coatings are made up of very thin slices of metallic, oxide, or rare-earth materials.

The thickness and relationships between these “slices,” similar but opposite to gel filters on a light source, determine their overall effectiveness. An extremely general way of thinking about this is to consider an Instagram filter. All a “filter” is is an adjustment to certain properties of an image. Lens coatings apply these adjustments in real-time as the image is created.

Another way to think of these coatings similarly to a pair of sunglasses in front of your eyes. What do sunglasses do? They cancel glare (to some degree) and light reflections and sometimes filter different types of light, allowing you to see in an augmented way that’s more comfortable or even more effective.

The main purposes of coatings on binoculars are:

1: Reducing glare
2: Improving total light transmission
3: Increasing contrast

Glare

Think of taking a photo with a bright light in the background. A bright light source will often create a flare or “ghost image” that can obstruct your view. With cameras, sometimes this effect is desirable, but not with observation optics! Hunters need the clearest view possible to make out minute details.

Often we find ourselves glassing toward the Sun, so certain coatings prevent reflections that lead to those flares. Most optics companies develop coatings for both the inside components of binoculars and the outer surfaces of their lenses. These work together to present the image that meets your eye. These coatings can vary by manufacturer, but they all are in pursuit of the same goals.

Brightness

Another reason to prevent as much reflection as possible is to maximize the amount of light that passes through the lenses and optical systems and into the user’s eye. Optics manufacturers spend decades developing ways to reduce the amount of “wasted” light.

This also applies to the effects of different combinations of coatings on internal and external components. The first time folks look through a Swarovski EL, their reaction usually goes something like this: “Holy cow! That’s so bright! It almost hurts my eyes!” That effect is common with many high-end binoculars. It may seem like optics are priced based on glass quality alone, but there are MANY factors such as these coatings that are lesser-known to many consumers.

Contrast

The biggest, baddest optic on the planet is utterly useless if the user can’t make out the details of the object they are looking at. Coatings related to contrast are all about color. Makers of hunting-specific optics apply coatings that can affect the relative dark and light portions of an image, allowing greater distinction between targets and backgrounds.

For example, Leupold’s Twilight Max HD coating (available in the BX-4 and BX-5 Pro Guide HD line) filters for certain colors (wavelengths) of light that are present at early dawn and dusk. This coating effectively filters certain colors and amplifies others so that details can be made out in low, orange-red lighting conditions. Leupold claims that their coatings can extend glassing or shooting light by up to 15 minutes. If you’ve ever taken aim just before sunset, you can surely appreciate the importance of that 15 minutes. Swarovski Optik’s SWAROBRIGHT coating has a similar effect. Their lenses are also coated to preserve the best possible image in very bright conditions with no “washing-out.”

Beyond the quality of the glass itself, the right coating can make a massive difference in what is perceived by the user. Higher levels of contrast can create advantages when trying to spot, for instance, a brown-grey-colored coues deer or mule deer against a brown-grey gravel backdrop. This is extremely helpful when glassing an area with lots of “rock deer” or branches that look just like antlers.

As we’ve said before, when buying any optic, the best way to find out if it works for you is to actually get your hands on it. It is important to note the treatment of the glass as well. Some folks prefer the stronger reds and blues of Leica or the specific dusk color strength of Leupold glass. Others prefer the strength of greens and yellows that are associated with Swarovski and Zeiss.

Not all eyes are the same, and not all products from one manufacturer are the same. There is a lot of info to know before you test drive your optics, and be cautious of your buddy who says he’s found a cheat code to finding more/bigger game. It’s all very personal.