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What Do the Numbers Mean On Binoculars? (Complete Guide)


You can see numbers like 10×50 or 20×60 on binoculars but do you know what these number means?

Model numbers on binoculars tell you their magnification power and the size of the lenses. In 8×42 binoculars, for example, “8” is the magnification power and “42” is the distance across (in millimeters) of the lenses.

Let’s discuss the numbers and specs of the binoculars in detail:

Understanding Binocular Specs


Binoculars are divided into small, medium, and full-size categories. This classification is because of the size of their objective lenses (the second number in the model name).
Note: That the varieties in optics, design and development imply that models with similar size objective lenses will be different in size and weight.

  • Small Binoculars: Objective lens size is under 30mm (8×25, 10×28, and so forth).
  • Medium Binoculars: Objective lens size is from 30mm to 40mm (10×30, 8×32, and so on).
  • Full-size Binoculars: Objective lens size is bigger than 40mm (8×42, 10×50, and so forth).

If you want to put binoculars in your bag pack. Then lightweight small models will be a good choice. Medium size models can give you more accurate pictures and be more friendly to hold for longer durations. That may change with bigger full-size binoculars, which are difficult to hold for a longer duration.

Magnification Power

Most of the time you’ll pick magnification between 8 or 10. However, you can as well find out models with lower or higher magnifications.

  • 8-power binoculars: A more wide field of view.
  • 10-power binoculars: A closer, more detailed view.
  • An 8×25, 8×32, and 8×42 pair of binoculars all give a similar magnification: An object will seem multiple times nearer than your naked eye.

A binocular with more magnification in every case is better but that is not generally the situation. Since magnification as well needs the use of your hands. Binoculars with magnification powers more than 10 are not easy to carry and move around with.

Field of View

Magnification power likewise directly affects your field of view. Lower magnification extends it; higher magnification limits it.
Having a smaller field of view can make it harder to find little and moving objects (like birds) when you zoom at them. That normal field of view allows in less light, so pictures will be slightly blurry.

Objective Lens Diameter

The width of the objective lenses plays a vital part in how much light your binoculars can get in. For two sets of binoculars, that in any case have the very same particulars, the pair with bigger objective lenses will catch more light, giving a more brilliant picture. Binoculars with more excellent optics will as well have more clear pictures.

Exit Pupil

A higher number offers a good quality of pictures. A higher number indicates a better view in low-light circumstances. And it will be simpler to keep a full picture of an object if your hands move or shake.
For 8×42 binoculars, 42 partitioned by 8 equivalents with an exit pupil width of 5.25mm.
It demonstrates the size of the beam of light that arrives at your eyes. Whose pupils change from about 2mm in more light to 7mm in complete darkness.
For low-light circumstances, an exit pupil of 5mm or more is acceptable. For sunny days exit pupil size is less significant because almost all binoculars offer exit pupil that surpasses 2mm.

Eye Relief

Eye relief is the distance between an eyepiece and your eye while the entire field of view is visible. This is a key spec if you wear glasses.
Most binoculars have flexible eyepieces that allow you to set them to their highest eye relief point.

Understanding the Optics of Binoculars

Lens Materials and Coatings

This is the place where trend-setting innovations become possibly the most important factor. The design of the glass and coating on the lenses make their reflection lesser to check the clearness and magnificence of your picture. This is why testing is very important.

Prism Type

The prisms are the optical components that pass the light from the picture through the binoculars to your eyes. Old fashion “porro prism” binoculars include wide barrels in the front that are not aligned with the eyepieces. More up-to-date “roof prism” models have eyepieces and objective lenses adjusted. The physical appearance of the binoculars doesn’t disclose to you anything about the optical quality, yet having roof prisms allows binoculars to be smaller and lighter.

Taking Care of Your Binoculars

Waterproof and Weather-Resistant Binoculars
If you’ll utilize your binoculars on a boat or in the rain. You’ll need to look at waterproof or climate-proof binoculars. Manufacturers usually provide the degree of water resistance as “waterproof”.
Waterproof binoculars usually use O-rings to seal out water. They can tolerate the rain. But they are unable to tolerate the excessive amount of water.
Climate safe (or water-safe) binoculars are not completely waterproof. They can deal with light rain, yet not a storm nor an excessive amount of water.

Rubber Coating

While it will not give full-scale crash endurance, a rubber coating is yet important to face minor knocks and falls. Through this, It is very easy to use binoculars in an open-air environment.

Fog Proof Binoculars

Binoculars can fog up when you move from a cold to a warm climate. This is a very irritating situation if humidity gets inside the binocular.
The manufacturer replaces the air with nitrogen. In this way, humidity inside the binocular is not collected. This secures against fogging up of the inward lens surfaces, not the outside ones.

Final Thoughts

What do the numbers mean on binoculars?  Now you know the significance of those numbers and what they mean. Having proper information about binoculars’ specs will help you choose the perfect one for you. It will also help you understand how it works and how you can take care of your precious set of binoculars.

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