Binocular Lens Coatings – What are they for?
October 12, 2009 by binocular
Binocular lens coatings are a common feature, but many people don’t particularly understand what they are, why they are needed, or what the descriptions of them mean when it comes to picking out a pair. They aren’t something you want to ignore though, as the coatings on your lenses can have a major effect on the overall viewing experience. Let’s examine the answers to each of these questions and see what that means for making a purchase decision.
Binoculars are made up of multiple different glass lenses arranged to direct light from the objective end (pointed at the subject) to the eye piece, where you are viewing the image. The unfortunate thing is that glass is not 100% perfect at transmitting light. Each glass surface will reflect some of the light that that strikes it, rather than passing it through.
As the image passes through each lens, this effect is additive and results in a significantly dimmer image reaching your eye than could otherwise be. Of course, you could simply graduate to larger objective lenses in order to compensate, but that will also increase the physical size and weight of the binoculars. A better solution is to simply increase the efficiency of the lenses that are already there.
That’s where binocular lens coatings come in. Lenses are coated with chemicals that reduce the light reflected, increasing the light that is allowed to pass through. Each one is a somewhat minor increase, but take altogether the light throughput can be increased by 50% or even more.
But the possibilities don’t end there – it turns out that the coatings can be layered on top of each other. Each additional layer decreases the light reflection even more, which has led many manufacturers to coat their lenses multiple times, sometimes 10 or even more layers. This is applied to each lens in the binoculars, bringing the percentage of original light transmitted astonishingly close to 100.
The result is that you get the most possible light with the least hardware, the least bulk, and the least weight to cart around. Look at it as an efficiently play. Uncoated lenses are wasting a significant portion of the light coming in, and lens coatings simply reclaim that potential. Since this process adds virtually no weight, doesn’t have a detrimental effect on visibility, and vastly improves the brightness of an image, there’s no reason not to go for binoculars with lens coatings.