What Do Binocular Numbers Mean


Binoculars are optical devices that consist of two parallel telescopes mounted side by side. They allow both eyes to observe distant objects simultaneously, providing a three-dimensional view. Binoculars are commonly used for a wide range of activities, including observing nature, sporting events, concerts, and even for maritime purposes.

Understanding the numbers associated with binoculars is crucial for choosing the right pair that suits your needs and preferences. These numbers represent various features and specifications that determine the performance and capabilities of the binoculars.

Understanding Binocular Numbers

Objective Lens Diameter

The first number in the binocular specification represents the objective lens diameter in millimeters. For example, if the number is “8×42,” the objective lens diameter is 42 millimeters. The objective lens is responsible for gathering light and plays a significant role in determining the brightness of the image. Larger objective lenses allow more light to enter, resulting in brighter images, especially in low-light conditions.

Magnification Power

The second number in the binocular specification indicates the magnification power. In the example “8×42,” the magnification power is 8. This means that the binoculars can make the viewed object appear eight times closer than it actually is. It’s important to note that higher magnification is not always better, as it can also lead to a narrower field of view and increased image shake if not stabilized.

Field of View

The field of view (FOV) is an important factor to consider when looking at binocular specifications. It refers to the width of the observable area when looking through the binoculars. The field of view is usually measured in feet at a distance of 1,000 yards. A wider field of view allows you to see a larger area, making it easier to track moving objects or scan a landscape.

Exit Pupil

The exit pupil is another critical aspect of binoculars that affects the viewing experience, especially in low-light conditions. It refers to the size of the beam of light that exits the eyepiece and enters your eyes. The exit pupil diameter is calculated by dividing the objective lens diameter by the magnification power. For example, in a pair of binoculars with a 10×42 specification, the exit pupil diameter would be 4.2 millimeters (42 divided by 10).

Close Focus

The close focus specification indicates the minimum distance at which the binoculars can focus and still provide a sharp image. It is particularly relevant for activities that involve observing objects at close range, such as studying insects, flowers, or other intricate details. Binoculars with a closer focus distance allow you to explore nearby subjects with enhanced clarity and detail.

Eye Relief

Eye relief refers to the optimal distance between the eyepiece and your eyes while still being able to see the full field of view. It is particularly important for individuals who wear eyeglasses or sunglasses. Binoculars with longer eye relief provide a comfortable viewing experience, allowing you to maintain a suitable distance from the eyepieces without sacrificing image quality.

Prism Type

Binoculars utilize prisms to correct the orientation of the image and provide a more natural viewing experience. There are two primary types of prisms used in binoculars: Porro prisms and roof prisms.

Choosing the Right Binoculars

Closed look of binocular

Selecting the right binoculars can greatly enhance your viewing experience and ensure that you have the best tool for your specific needs. Here are some essential factors to consider when choosing the right binoculars:

Determine Your Purpose

Before purchasing binoculars, it’s crucial to determine your intended use. Are you planning to use binoculars for birdwatching, stargazing, wildlife observation, hunting, or general outdoor activities? Different activities have varying requirements for magnification, field of view, and other features. For example, birdwatching enthusiasts often prefer binoculars with a wider field of view, while stargazers may prioritize higher magnification.

Consider Your Budget

Establishing a budget range will help narrow down your options. Binocular prices can vary significantly based on the brand, quality, and specific features. Determine how much you are willing to invest in a pair of binoculars and look for models within that price range. It’s worth noting that higher-priced binoculars often offer superior optics, durability, and additional features, but there are also excellent options available at more affordable prices.

Test and Compare

Whenever possible, try out different binocular models before making a purchase. Visit a store that specializes in optics or attend events where you can test various binoculars. Pay attention to factors like comfort, ergonomics, weight, and ease of focus adjustment. Testing binoculars hands-on will give you a better understanding of their performance and help you make an informed decision.

Ergonomics and Comfort

Since you’ll be holding the binoculars for extended periods, ergonomics and comfort are essential considerations. Look for binoculars that feel comfortable in your hands and have a nonslip grip. Adjustable eyecups can be beneficial, allowing you to customize the eye relief to suit your needs. Also, consider the weight of the binoculars, especially if you plan on carrying them for long distances or extended periods.

Durability and Weather Resistance

If you anticipate using your binoculars in rugged environments or during inclement weather conditions, durability and weather resistance become crucial factors. Look for binoculars that are built with sturdy materials and have features like waterproof or fog-proof construction. These features ensure that your binoculars can withstand the elements and provide reliable performance even in challenging situations.


Choosing the right binoculars involves considering factors such as your intended purpose, budget, ergonomics, durability, and weather resistance. By understanding your specific needs and researching different models, you can make an informed decision and select binoculars that will enhance your viewing experiences for years to come.

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