Binocular is a widespread word, and everyone knows what a Binocular is. But the numbers we see on a binocular or the terminology of a Binocular is relatively unknown for beginners. Even then, The first thing you need to know before buying Binoculars is the significance of the terminology and the numbers we see on it. Because there are various types of Binoculars, these are made for different kinds of uses, like you may want to use them for birding, hunting, astronomy, boating, or wildlife viewing. So, the numbers matter. This article will show you the significance of these numbers. We will show it understandably; thus, you can understand it very quickly.

There are many facts to know, like magnification – numbers, size of lenses, viewing-angles, exit – pupil – numbers, eye – relief – numbers, the – field – view, focusing. We will give you the ultimate idea about everything related to numbers and terminology of a Binocular one by one.

## What is Meant By Magnification Numbers?

When you buy a Binocular, at the very first, you see some numbers like 10×50 or 12×60. Seeing these numbers, you feel like these are significant numbers, but the problem is, you don’t know the significance of these numbers.

Here, the primary number, such as 10x & 12x, defines the strength of magnification. More magnification power helps you to see the object more closely. Here, 10x means you will see the object ten times closer than its actual distance, and 12x means you will see the object 12 times closer than its actual distance. The eyepiece magnifies the distance between the binocular and objects.

But with more magnifying power comes difficulty in controlling the steadiness. So, you have to use some support to get much stability for the Binoculars with ultra magnifying power. You can adjust the magnifying power manually with zoom binoculars.

## What is Meant by the Numbers After the Magnification Number?

The number after the magnification number refers to the size of the objective lens. It is also called an aperture. A common word, right? It is a common word for the camera section. Yes, cameras and Binoculars both work with lenses. You can know the lens size of your pair of binoculars by these numbers.

**For example,** In a Binocular with 12×60 numbers, there will be 60mm objective lenses in it. So, this number defines your binocular lens size. With bigger lenses, your binocular will look more prominent. If you want to see a brighter image, you will need bigger lenses. You know that objective lens diameter collects the lights. So, the bigger aperture will give you better image quality. Again, if you want to see the night sky, a more significant objective diameter will help you better image quality because the aperture’s job is light gathering.

So, the numbers after the magnification numbers define the sizes of the objective lenses. The numbers can vary and the size of the lenses as well. You have to choose your Binocular according to your needs.

## Confusion Regarding Magnification Number and Aperture

Still, the numbers can confuse you. Like, you may think that what numbers between 12×40 and 12×60 will be better to see the beautiful sky at night? As we discussed earlier, 12x defines how close the object will be, and 40, 60 defines how clearer, brighter, and broader the image will be. So, it’s clear that 12×60 will give you more superior viewing experiences and be better for night sky watching and daylight viewing.

## AoV & FoV: What does it mean by Angle of view and Field of view?

We will explain the angle of view first, then the field of view, and after completing the explanation, we will clear your confusion between them.

- The angle of view is described in degrees. It refers to the amount of horizontal view you will be able to see by your binocular. More degrees will allow you to see a broader picture. If you want to get the right viewing angle, the degrees should be more than 6. Sometimes, you may see some higher numbers. No tension. Here the company used the actual amount of AoV. For example, you may see 90 degrees, but the manufacturer multiplied the Aov with the Magnification number of Binoculars.
- For Instance: a 12×60 binocular with 7.5 degree Aov will get 90 Degrees actual AoV by multiplying (7.5 x 12 = 90).
- The main difference between Aov and FoV is, Aov is written in degrees, whereas Fov is in feet or meters. But both of them refer to the same thing, the size of the image you will see from your binocular. So, the higher field of view means that you will get a bigger picture. But don’t forget that more powerful magnification will decrease the viewing field because more magnification gives you a closer view. If you want to watch it closely, you will get a limited small view. More than 300 feet is enough FoV for Binoculars.

### Confusion:

We have seen that the purposes of the angle of view and field of view are quite similar. Though they are not the same, you can convert Aov into FoV. To convert Aov into Fov, you need to multiply the Aov by 52.5.

**For example:** suppose your Aov is 7.5 degrees; you want to convert it into FoV, then multiply it with 52.5.

52.5 x 7.5= 393.75. So, here the field of view is 393.75.

## What is Exit Pupil Diameter?

EPN (Exit pupil – number) defines the amount of light that sees the object. It is essential because you need perfect light to see any particular images. To know the exit pupil size, you have to divide the objective lens sizes with magnification numbers.

For instance: You have a 12×60 Binocular. The exit pupil number is 5 (60/12 = 5). Or, to compare the sizes between two binocular, you can see the difference by merely holding them together. But I think the calculation is the more comfortable and perfect process to know the numbers of exit pupil size. Try to get a Binocular with a more considerable amount of exit pupil numbers. But most of the time, more than 4mm is okay. More exit pupil diameter is better for low light conditions because it gives you more lights to see the objects.

## What is the Closest Focus distance Number?

Above, we discussed how far you can see, how much brighter afar image can be, and how wider you can see. But another important thing you need to know for getting a bright image quality is the minimum focus distance? The minimum focus distance to focus is around 4 meters.

## What is Eye Relief?

This ERN (eye relief – number) is essential for the people who wear glasses. It informs your eyes distance from the eyecups and helps you to adjust it. 15mm eye relief is enough. So before buying, confirm that it has enough eye relief if you wear glasses because the image quality also depends on eye relief distance (number).

## Type of prism: What are the types of prism used in Binoculars?

Manufacturers use a different type of prism design as optical elements in a pair of binoculars. Porro prism mirrors and Roof prism mirrors are two prism type.

## Final Words

Now, you are familiar with the numbers and the terminology of a binocular. Remember these tips in short: you will get less FoV with more significant magnification, big objective lenses are useful for the low light condition, ensure higher than 4mm exit pupil number for enough light to see. If you are a beginner and not an expert binocular holder, you are requested to avoid more than a 12x magnification number because a powerful binocular can hamper your viewing experiences. We hope now you have got a clear idea about Binocular numbers and terminology. Now you can buy a binocular like an expert. Thank you.

I am an enthusiastic student of optics, so I may be biased when I say that optics is one of the most critical fields. It doesn’t matter what type of optics you are talking about – optics for astronomy, medicine, engineering, or pleasure – all types are essential.

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