What Do the Numbers on Binoculars Mean?

If you’ve ever tried to shop for binoculars, you’ve probably noticed that they come with a bewildering array of numbers and specifications. Do you wonder what those numbers on them mean? Those combinations of digits and symbols can be quite confusing for those unfamiliar with the technicalities of optics. 

Fear not, as your confusion is going to end in today’s guide as I will break down the numbers and explain how they describe the specification of binoculars. I am sure that by understanding the specifications of binoculars you will be able to select the right pair for your needs.

So, let’s dive into the world of binoculars and talk about those numbers that might be confusing you. By the end of the article, you’ll be equipped with all the technical knowledge of optics: and you’ll be able to make informed decisions about binos.

Related Article: What Do 30X60 Binoculars Mean?

Understanding Numbers on Binoculars

Before I go down into the explanation, let me answer the question: what do the numbers on binoculars mean? Two main numbers explain the specification of binoculars. The first number represents the magnification number whereas the second number represents the objective lens size.  

Apart from these two numbers, you’ll see some other numbers including eye relief, the field of view, close focus, and exit pupil which have a bigger impact on the performance of binoculars. Knowing the meaning of these numbers will help you understand the capabilities of binos.

If you’ve already used or bought binoculars, then you will be well aware of those numbers written on the box of binoculars. But many people don’t know what they mean. Without knowing or having knowledge about those numbers, you can’t choose the right pair.

Look, as said earlier, the number of binoculars represents the specification. So, when you don’t understand numbers, then actually you don’t understand the specifications and then you make the wrong call by choosing useless binoculars that do fit your needs. Not to forget, each outdoor activity requires specific binoculars.

For example, for stargazing, you will need binoculars with higher magnification power and objective lens size like 20×50, and for bird watching, you will need 8×42 binoculars. So, understanding numbers informs you about the capabilities of binoculars. So, let’s dive deeper and understand those numbers.

Read More: What Does 7X50 Binoculars Mean?

1- Magnification

When it comes to binoculars, one of the most important numbers you’ll see is magnification. This number is written on the box and body of almost every binoculars. If you have ever seen the box, then you know that two numbers represent the binoculars’ specifications 8×42 or 10×50.

The first number in this specification represents the magnification power and it defines how big visuals you will see through the barrel of binoculars. Magnification is the amount by which an object appears larger or bigger.

For example, if you are looking at a bird through binoculars with a magnification of 8x, the bird will appear eight times bigger as compared to when you see it without using binoculars.  Keep in mind that the higher the magnification, the closer and larger the object appears.

2- Objective Lens Size

The objective lens is the lens at the front of the binoculars that gathers light and directs it to the eyepiece. The size of the objective lens is measured in millimeters. But the question is how to know about the size of an objective lens by understanding the numbers. 

Suppose you have binoculars with several 10×42, the objective lens size is 42 millimeters. The second number in the specification of binoculars represents the objective lens size.  Keep in mind that the size of the objective lens determines how brighter or sharper visuals you will get.

The larger objective lens will allow more light to enter the binoculars, which makes for a brighter and clearer image and vice versa. If you’re buying binos for low light conditions, such as at dusk or dawn then make sure that you choose a binocular with a bigger sized lens like 50mm or more than that.

Also Read: What Does 7X35 Mean on Binoculars?

3- Field of View (FOV)

The field of view is another important factor that you should know. It is the width of the area that you can see through the binoculars, and it is typically measured in feet or meters at a certain distance. Generally, it is measured in feet.

Suppose you have binoculars with a FOV of 300 feet then it means that when you look through the binoculars, you can see 300 feet across at a distance of 1000 yards. 

Let me give you another example for more clarity. If the FOV of binoculars is listed as 400 feet at 1000 yards, it means that you can see a width of 400 feet when looking at an object that is 1000 yards away. Binoculars with different fields of view are available in the market like 250 feet, 300 feet, 350 feet, etc.

Are you thinking about why FOV is so important? It has special importance because it can help you determine how much of the scenery you can see at once. A wider FOV means that you can see more of the scene in front of you, while a narrower FOV means that you’ll have a more limited view.

The requirement of the field of view for different binoculars varies. For example, if you are using binoculars for hunting and bird watching then you will need a wider FOV so that you can keep track of moving animals. 

On the other hand, if you’re using binoculars for stargazing, you might not need as wide of a FOV since the stars don’t move as quickly. For these activities, you will need a narrower field of view with higher magnification power.

Learn More: What Does 8X32 Binoculars Mean?

4- Exit Pupil

No, I am not stopping here as there is a lot to come. So, relax, sit back, and keep reading. I know that these numbers can seem like a jumble of confusing digits, but they provide valuable information about the capabilities of binoculars. 

The next number that provides useful information about the binoculars is their exit pupil size.

The exit pupil is the diameter of the beam of light that exits the eyepiece of the binoculars. Keep in mind that the bigger the exit pupil, the brighter the image will appear, particularly in low-light conditions. 

To determine the exit pupil, simply divide the diameter of the objective lens by the magnification of the binoculars. For example, if you have 8×42 binoculars, the exit pupil would be 5.25mm. Below is the method of finding the exit pupil.

Exit Pupil = 42/8 = 5.25

Suppose you have 10×50 binoculars then the exit pupil will be 5 mm.

Why is the exit pupil important? Well, this exit pupil actually puts a massive impact on the brightness of visuals you get through binos.  If the exit pupil is smaller than the size of your eye’s pupil, you won’t be able to see the full brightness of the image. 

So, what’s the ideal exit pupil size? It depends on how you plan to use the binoculars. If you’re primarily using them in bright daylight conditions, a smaller exit pupil (around 2-3mm) will be perfectly fine.  But if you’re using it in low light conditions, you’ll want a larger exit pupil (around 5-7mm) to maximize brightness. 

5- Close Focus

Close focus is another important that describes the minimum distance at which the binoculars can focus clearly on an object. This is very important for those binoculars which are used to observe the details of small creatures like insects, and butterflies.

Keep in mind that the close focus distance is usually listed in feet or meters, and it’s important to choose a pair of binoculars with a close focus distance that suits your needs.

If you’re planning to use your binoculars to watch birds at a feeder, I recommend you to go with close focus distance of 6 feet or less. This will allow you to see the birds up close and in detail, even if they are perched on a nearby branch. 

On the other hand, if you’re buying binoculars to view distant objects like stars shining in the sky, then the close-focus readings won’t be important for you. This reading or number is only important when you’re viewing smaller objects that are very close to you.

Close focus is also very important for indoor activities, such as attending concerts or sporting events. With a close focus of just a few feet, you can get a great view of the performers or players, even if you are sitting near the back of the venue.

Related Article: What Does 12X50 Binoculars Mean?

6- Eye Relief

In my previous guide, I have already explained eye relief and the importance of binoculars. However, it is the distance between your eye and the binocular eyepiece that allows you to see the full field of view. Eye relief is always measured in millimeters.

Eye relief is especially important for people who wear glasses, as they need more space between their eyes and the eyepiece. If the eye relief is too short, they won’t be able to see the full image and may experience discomfort or eye strain. 

Eye relief above 15 mm is considered ideal: however, some binoculars come with eye relief below 15 mm which I don’t recommend you buy as you won’t get a perfectly pleasing viewing experience with that level of eye relief. 

To determine the eye relief of your binoculars, simply look for the number marked on the binoculars or in the product description. This number will typically be listed in millimeters, such as “15mm eye relief”.

Conclusion

So, I hope that you have a better understanding of binoculars and their meanings. Unfortunately, it is a fact that people don’t have much knowledge about the technical aspects of binoculars. If you don’t know numbers, I challenge you that you won’t be able to find suitable binoculars for your activities.

In this guide, I have listed all those numbers and explained why they are so important to ensure that you get satisfying knowledge and keep yourself safe from making wrong decisions. With the hope that this guide will add value to your life, I am signing off! See you with another useful guide.