So you have decided to buy your first pair of binoculars, which is exciting. But before you break open the piggy bank, there are a few things you need to know. Key among them, what do the numbers on binoculars mean.
Binoculars have several numbers printed on them. These numbers are meant to give you the buyer a wide range of information about the binocular you are about to buy.
That being said, in this article, we will be discussing what do binocular numbers mean.
Binocular Magnification Meaning
When you look at a binocular, you will notice a number consisting of two figures. For example, 8×40 or 10×50. So what exactly does this number mean and what does it say about the binocular.
This number is representative of a binoculars’ two most important features, magnification and objective lens.
The first number refers to a binoculars’ magnification level. As such, a 10x binocular can make an object appear ten times closer than it is. The higher the number, the nearer objects will appear.
That means a 12x binocular will make objects appear closer than a 10x one. Of worth noting is that a high magnification of 12x and over makes it difficult to maintain a steady image. The solution is to stabilize the binocular on something stable, such as a tripod.
So how far can you see with 10×50 binoculars? A 10x magnification will be sufficient for observing objects about 2KM away. However, for spotting things 3km or more away, you will need a higher magnification of about 16x or 20x.
The second number that follows the magnification denotes the size of the binoculars’ objective lens. The objective lens is located on the other side of the eyepiece you use to look through the binocular.
Therefore, a 10×50 binocular has an objective lens with a 50mm diameter. The wider that lens, the heavier the binocular. Also, a wider objective lens means more light passing through it. As such, a 10×50 binocular will be better for night time viewing than a 7×35 one.
Angle of view
The next two numbers you are likely to notice printed on binoculars are for the angle of view and field of view. The binocular numbers definition for these two numbers is mostly the same. The angle of view is usually indicated in degrees.
These two numbers refer to the amount of horizontal area that is visible through binoculars. Most of the best birding binoculars under 200 will have an angle of view of 6 degrees while some will have a high number such as 72 degrees indicated.
However, this is usually the actual angle of view and is got by multiplying the magnification with the angle of view. For example, if a binocular has a 10x magnification and an angle of view of 7.2 will have an actual angle of view of 72 degrees.
On the other hand, the field of view is indicated in feet per 1000 yards or meters per 1000 yards. A higher number means you have a wider horizontal view. A field of view of 300 to 375 is sufficient for most people.
It is possible to convert the angle of view to the field of view. This is done by multiplying the angle of view with 52.5. That means an angle of view of 7.2 degrees translates to a 378 field of view.
Field of view
The field of view is the same as the angle of view. What is important to note is that the field of view is affected by an increase in magnification. Therefore, higher magnification will result in a narrower field of view.
This raises the question of what does 10×50 mean in binoculars, especially in relation to the field of view. While the field of view is affected by magnification, it is usually in relation to the objective lens size.
Therefore a 7×35 binocular will have a wider field of view than a 10×50 one.
The exit pupil number is another you are likely to find on a binocular. This one is usually measured in millimeters e.g., 3.1 mm. To understand the exit pupil, you need to hold a binocular about 8 inches away from your eye.
You will notice two dots at the center of the eyepiece. This is where the light from the lenses hits your eyes to allow you to see an object.
The best Binoculars under 100 will have an exit pupil of 4 inches or more. The exit pupil number is obtained by dividing the objective lens size and magnification. For example, a 10×50 binocular will have an exit pupil of 5mm.
This particular number is essential to glass wearers. The eye relief is how far you can be from the binocular’s eyepiece and still see the binoculars’ whole field of view. Similar to the exit pupil number, this one is also indicated in millimeters.
A good Night vision binoculars will most likely have an eye relief of 8 to 10mm. This is a good enough eye relief for glass wearers. Essentially, the higher the eye relief, the better the binocular.
Binoculars are designed for seeing far off objects. Therefore, they do not do well when it comes to close distance objects. However, if you want binoculars for bird watching, you will probably want to get a clear view of relatively close birds.
This is where close focus comes into play. The narrow focus is the minimum distance a binocular can focus on. For example, a close focus of 13 feet means you will be able to see objects that are at least 13 feet away from you.
For some people, this number is not necessary, but for others, it is. In this regard, Rangefinder binoculars designed for hunting have a close focus of 15 feet. However, some birdwatching models have a close focus of up to 6 feet.
In this article, we have discussed the binocular numbers, meaning of the most important figures. These are the numbers that will help you know what a binocular is good for. For instance, a binocular with high magnification is excellent for astronomy.
Contrastingly a binocular with a close focus is ideal for birdwatching. On the other hand, a wide field of view is essential for hunting and birdwatching purposes.