Despite the great popularity of zoom binoculars, to many buyers, it’s still mysterious how they work, what makes certain models better (or different) than others, and what all the numbers mean. In today’s blog post, I’ll talk specifically about that – about the specifics of zoom binoculars and how they operate. I hope I’ll clear things up for you before making your buying decision so that you can rest assured you’re choosing the right pair for your needs.

Oftentimes referred to as “variable zoom binoculars” these devices allow you to “zoom-in” and “zoom-out” – pretty much like you would with a standard camera. Their main advantage is that they can achieve multiple levels of magnification. However, the size of the objective lens does not change. What this means is that as you increase magnification, you decrease the diameter of the exit pupil, which consequently results in a darker image. With zoom binoculars, the magnification power is there when you need it, however, the resulting images at high magnification may be a bit dim and unstable.

Nevertheless, regardless of that, if you plan most of your viewing to be at low magnifications, but you still want to have the option for occasional up-close viewing, then, by all means, buy zoom binoculars. If, on the other hand, you plan on using high levels of magnification frequently, your best bet is to consider buying higher powered binoculars with appropriately sized objective lenses for comfortable viewing.

What you may not have known about zoom binoculars is that they’re actually two independent telescopes connected together. They need to maintain a kind of synchronization between the two scopes, consisting of a moving lens element within each eyepiece. This is usually achieved by a flexible metal band that’s known as a “Zoom linkage band”. It passes through the ocular arms to connect the zoom mechanisms on both sides together.

Due to the great number of minute, moving parts, it is either impossible or extremely difficult to get both scopes properly aligned, which is why collimation problems often occur. As the lens elements move, each image will shift slightly, and although this wouldn’t be noticeable in a monocular, your binoculars will end up never being in the ideal alignment. Generally, if having zoom functionality is extremely important to you, you can instead buy a pair with fixed magnification binoculars. They will be less versatile when compared to zoom binoculars, but they will provide you with a better viewing experience.