How Do Binoculars Work?

Most of us have used them. Many of us own them. But the majority of us have no clue as to how binoculars work. Well, read on and we will show you the magic behind the lenses.

Binoculars are a very useful tool. They have a range of uses and applications such as sporting events, hunting, and surveillance. If we were to list all of the uses, you may need to cancel all of your plans. The list is almost endless. Just about every hobby and outdoor activity has employed binoculars at some point.

As you know, binoculars allow us to see far distances with intricate detail. But, how do these contraptions let us see something that is miles away as if it was right in front of us? Well, let’s clear things up and look at how the lenses of binoculars magnify an image to present us with a crisp and clear viewing experience. 

How Do Binoculars Work

Binoculars: How do they work? 

Binoculars are simply two small telescopes mounted side by side. The center of these two scopes is hinged so they can be separated and maneuvered to fit all different sizes and shapes of faces. The main components of binoculars include:

  • The focus
  • The diopter
  • The ocular lens
  • The adjustable eye cap
  • The objective lens 

The objective lens is what takes in light to capture an image. The ocular lens magnifies the image so that it becomes clearer for your eye to see. To discover how binoculars function, let’s study how binoculars use lenses.

Binocular lenses 

The lenses of binoculars come in all shapes and sizes. Their job is to focus light rays away from certain objects so you can easily see distant sites more accurately.

Refraction is the key to how lenses function. This is the way that light bends as it transfers from air to another different material such as glass or water. Without refraction, the lenses wouldn’t work. Without lenses, your binoculars wouldn’t work.

Take a glass of water, for example. When water sits in a glass, it appears to have a straight upper edge. This is despite its ever so slightly curved surface (known as meniscus). If you place a clear glass of water on a newspaper and look down through it, the news print will look the same as usual.

This is because the top of the water is relatively straight. However, if this water’s upper surface was curved, the newspaper’s print would become magnified and larger.

This is similar to how a lens works. These curved pieces of glass are shaped a little like a lentil. Believe it or not, lens gets its name from the Latin word for “lentil.”

As light rays hit a glass lens, they slow down and bend. If the lens has a curve, like a dome, it’s known as a convex lens. When light rays enter convex lenses, they bend in toward the direction of its middle, almost as if the lens is sucking the rays in.

This means that convex lenses bring distant light rays into a better focus. These lenses are also called converging lenses as they make light rays converge (come together). As you look through a convex lens, the image you see appears larger.

So, what about binoculars? Let’s take a look at the optics of this tool.


If you want to see something in the distance more clearly, grab those binoculars. Thanks to the convex lenses which we mentioned above, you are able to see the details of a tree from far away. 

In binoculars, two convex lenses are placed one in front of the other. The first lens catches light rays from the distant items and then makes a focused image just a short distance behind the lens. 

This lens is called the objective as it’s the closest to the object you are looking at. Then, the second lens gets to work. This picks up the image and magnifies it, just as a magnifying glass magnifies images on paper. This is called the eyepiece.

If you place two lenses together in one closed tube, you have yourself a telescope. Binoculars are essentially two telescopes side by side. One for each of your eyes.

However, when light rays from a distant object travel through a convex lens, they are capable of crossing over. If you’ve ever noticed that distant objects appear to be upside down when looking through a magnifying glass, this is why.

The second lens doesn’t help in this instance. That is why binoculars have a pair of prisms which are large pieces of glass. These are located inside and work at rotating the image through 180 degrees. Check this if you need hvac services. One prism will rotate the image through 90 degrees while the other rotates it another 90 degrees. In other words, the prisms effectively turn the image upside down.

Because there are two tubes in binoculars, there are four prisms tightly packed inside as you look down the tubes. And these unusual tube shapes look like this because they need to house two prisms inside.

These prisms are why binoculars are often quite heavy and chunky around their middle. On the other hand, field glasses are much lighter and compact because they flip incoming images using only their lenses. No prisms are needed but the image quality tends to be poorer.

Different sizes

There are different sized binoculars to suit different occasions and activities. These include:

  • Compact binoculars 
  • Midsize binoculars
  • Full-size binoculars

Compact models are ideal for adventurers who are always on the go but these do not magnify images as well. Midsize binoculars have good to very good magnification qualities and have the widest range to choose from. Full-size binoculars are best for specific situations such as bird watching and are the most powerful.

In Summary

With quite simple technology, binoculars allow you to see more than you’d ever see with the naked eye. Simple but ingenious, remember how your binoculars work the next time you’re using them.