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What Do Binoculars Numbers Mean?

Last Updated: 03.06.20

 

If you want to take up a hobby that requires the use of binoculars such as hunting, bird watching, or other outdoor activities, you can read more about this type of product in our recent article. However, before you get to the point of actually purchasing binoculars, you should know more about their features. 

One of the most puzzling characteristics of binoculars is the fact that they are provided with a series of numbers. To understand how binoculars work, you have to be aware of what those numbers represent, and this is what we’re going to focus on right now.

Magnification and Objective Lens Size

Once you start looking for binoculars, whether you decide to make your purchase in a shop or online, you will see that all the models are provided with two numbers looking like this ‘8×42’. The values may differ, of course, and what they represent is essential in order to understand what type of view you can get from those binoculars.

The first of these two numbers refers to magnification and the second one refers to the diameter of the objective lens. These words might not mean a lot right now, but don’t worry, we are going to explain in detail what these features are.

When talking about binoculars’ magnification, which is often called power, we refer to the device’s capacity to help you perceive the objects situated at a distance. You are going to use binoculars to get a better image of the objects that lie ahead of you and are difficult to perceive with the bare eye. This is where magnification steps in by making the object’s image larger and allowing you to see it clearly as if you were next to it.

Magnification is the first number in the pair and it is followed by the symbol ‘x’. This is not a random choice as the ‘x’ sign also has a meaning. In our example, we said the binocular has a magnification of ‘8x’. By using this particular device, you will get an image that is eight times larger than what you would normally get by looking at the view in front of you with the naked eye.

To give you a concrete example, imagine you are out in the woods, looking for your catch and you see a deer in the distance. You are aware that the animal is in front of you, but it’s hard for you to observe it with precision, let alone shoot it. You, therefore, use your ‘8×42’ binoculars and you see the deer’s image eight times larger. 

You now have a clear understanding of its features and the precise spot where it stands.

Not all binoculars are provided with the same magnification. In our example, we had a value of ‘8’, but there are other models that have a magnification of ‘10’ and can, therefore, provide an image that is 10 times larger.

Nonetheless, there are also some binoculars that express their magnification as a range, not as a single number. Consequently, such items will have their magnification and lens size expressed in a series that contains three numbers, for example, 10-20 x lens size.

This type of magnification is associated with zoom binoculars that allow you to adjust your device’s magnification according to the provided range. Thus, the 10-20 model enables you to choose a magnification that’s somewhere between 10 and 20.

Nonetheless, magnifying the image a lot, which works just like zooming in on a photo, might affect your capacity to observe your target and fulfill your goal. That is why it is not always essential to get binoculars that have a high magnification. In fact, a typical 8 or 10 value works well for most common purposes.

Let’s focus now on the second essential number – the size of the objective lens. This number is expressed in millimeters. The 8×42 binoculars we used as an example have an objective whose diameter measures 42 millimeters.

This diameter is important because it determines how efficient the binoculars are. In short, the surface of the objective lens is responsible for capturing the light. This is the interface between your eyes and the object you are trying to observe. The light is then transmitted to the ocular lens and your eyes.

An objective lens that has a larger diameter will be able to capture more light. This means that the object will appear brighter and you will be able to observe its details easier, which is what you want from your binoculars. Especially if you use your binoculars in an area or time of the day when there isn’t sufficient light, a large objective lens can enhance your viewing experience.

The bottom line is that a large objective can provide you with a brighter and clearer image that will help you do whatever it is that you’re trying to. Nonetheless, there is a problem that comes along with getting binoculars that have a big objective; they are heavier. 

This might make them inefficient for outdoor activities because you don’t want to carry heavy things with you when you go hunting or explore nature, you already have other gear and your heavy backpack.

This being said, depending on your purpose and how far you have to travel when you engage in the activity that requires binoculars, you might not want to opt for an item that has large lenses which make it hard to carry. According to most users, the standard 42 value is considered a good option for most activities.

With such a device, you should be able to get the quality image you seek while avoiding the burden that comes with carrying heavier binoculars.

Angle and Field of View

The lens size and the binoculars magnification numbers are essential when you want to purchase good binoculars. However, these are not the only numbers you will encounter when you read each product’s description. Two other important values are the angle of view and field of view, and they are intrinsically connected to how binoculars work.

Basically, both these notions refer to your binoculars’ ability to provide you a horizontal image. When you look through your binoculars, this is how you see the area that you want to explore. However, these are two different values, expressed in different ways.

The angle of view is also known as AOV and you will find it expressed in degrees. This number refers to the binoculars’ capacity to allow you to get a wide image and, consequently, to explore a larger area. Therefore, the higher this value is, the better your capacity to observe the areas you want to explore. 

A value of at least six degrees is necessary in order to get sufficient angle of view and anything that goes beyond this number is even better.

When you start looking for binoculars, you will realize that there are also products that come with a very large angle of view that’s more than 10 times bigger than the 6 degrees value. In this case, the manufacturer refers to the object’s actual AOV, which is a value obtained from the multiplication of the binoculars’ AOV with its magnification. 

Therefore, you can get the angle of view by deducting the magnification’s value from the actual AOV expressed in degrees.

The field of view, on the other hand, is measured according to the image you would get if you were at a distance of 1000 yards from the object or area you want to explore. The field of view also refers to the binocular’s capacity to offer coverage for a given area and provide you a horizontal view of that area.

Our eyesight also has a field of view or FOV and this refers to the horizontal image our eyes are able to capture from side to side. FOV may be expressed in feet at 1000 yards or it may be expressed in meters at 1000 meters. The higher the value of your binoculars’ FOV, the larger the horizontal view you will get.

One aspect you shouldn’t overlook, however, is that FOV and magnification are linked and the higher the second is, the lower the first one will be. Basically, the more you magnify your image in order to observe a certain target, the smaller the FOV becomes as the target is brought closer. Therefore, since most outdoor activities require an optical device that provides coverage for a larger surface, binoculars that have a better FOV are more suitable than those with large magnification.

All in all, purchasing the right binoculars is not easy if you really want to understand how these devices work. Nonetheless, with the information in this article, you are now able to make a choice, being aware of what binoculars numbers mean. Afterward, when you start using your binoculars, you will have plenty of time to truly understand their functionality.

 

 

Ioana Moldovan

Ioana’s professional experience in the optics field has helped her understand the value of passing her knowledge forward. Her curious personality helps her gather useful information for her readers and her goal is to make technical information fun and accessible to everyone.

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