If you’ve ever looked at a pair of binoculars, you’ve seen a set of numbers like 8×42 or 10×50. Understanding what do the numbers on binoculars mean is the key to choosing the right pair for your needs. These figures aren’t just a model code; they tell you exactly how the binoculars will perform in the field, affecting brightness, field of view, and stability.
This guide will explain those numbers in simple terms. You’ll learn how to interpret them and make an informed choice for birdwatching, sports, or astronomy.
What Do The Numbers On Binoculars Mean
The main numbers on binoculars, such as 8×42, represent two critical specifications: magnification and objective lens diameter. They are always presented in the format “Magnification x Objective Lens Diameter.” Let’s break down what each part means for you.
The First Number: Magnification (The “Power”)
The number before the “x” is the magnification. It tells you how many times closer the subject will appear compared to your naked eye.
- An 8x magnification makes an object look 8 times closer.
- A 10x magnification makes it look 10 times closer.
Higher magnification isn’t always better. While it brings subjects closer, it also amplifies hand shake, making the image shakier. It often means a narrower field of view. For general use, magnifications of 8x or 10x are the most popular and versatile choices.
The Second Number: Objective Lens Diameter
The number after the “x” is the diameter of the front (objective) lenses, measured in millimeters. This is a crucial factor for image brightness.
- Larger lenses (e.g., 42mm, 50mm) gather more light. This results in a brighter, clearer image, especially in low-light conditions like dawn, dusk, or forests.
- Smaller lenses (e.g., 25mm, 32mm) make binoculars more compact and lightweight, but they gather less light.
The combination of these two numbers defines the binoculars’ core performance. An 8×42 model offers a stable view with good brightness. A 10×50 model brings things closer and is excellent for low light, but will be heavier.
Other Important Numbers and Marks
You might see other specifications listed. Here’s what they mean:
Field of View
This is the width of the area you can see through the binoculars, usually expressed in feet at 1000 yards or degrees. A wider field of view makes it easier to follow moving subjects like birds or athletes. Generally, lower magnification and larger lenses contribute to a wider field of view.
Exit Pupil
This number (in millimeters) indicates how bright the image will appear to your eye. You can calculate it by dividing the objective lens diameter by the magnification (e.g., 42 ÷ 8 = 5.25mm).
- A larger exit pupil (over 4mm) is better for low-light viewing.
- It also makes it easier to find and maintain the image, which is helpful if your hands are unsteady.
Close Focus
This is the minimum distance at which the binoculars can focus on a subject. It’s important for viewers interested in butterflies, insects, or other close-up details. Some models can focus as close as 5 or 6 feet.
Eye Relief
Measured in millimeters, eye relief is the distance from the eyepiece lens to your eye where you can still see the full image. This is especially important if you wear glasses. Look for eye relief of 15mm or more for comfortable use with eyeglasses.
How to Choose the Right Numbers for Your Activity
Matching the numbers to your primary use makes all the difference. Here’s a quick guide:
Birdwatching and Wildlife
- Recommended: 8×42 or 10×42.
- Why: These offer an excellent balance of magnification, brightness, and a reasonably wide field of view for tracking animals. The 8×42 is often considered the ideal all-around choice.
Hiking, Concerts, and General Use
- Recommended: 8×32 or 10×32.
- Why: These are more compact and lighter than 42mm models, making them easier to carry for long periods while still providing good performance.
Astronomy and Low-Light Viewing
- Recommended: 10×50 or higher.
- Why: The large 50mm objective lenses capture maximum light for viewing stars, planets, or wildlife at dusk. A tripod is often recommended for magnifications above 10x.
Maritime and Sporting Events
- Recommended: 7×50 or 8×42.
- Why: The 7×50 configuration offers a very bright image, a wide field of view, and exceptional stability on a moving boat. For daytime sports, an 8×42 is superb.
Putting It All Together: A Simple Selection Checklist
- Decide your main activity. Use the guide above to narrow your starting point.
- Consider magnification. Choose 8x for a steadier, wider view. Choose 10x for more detail at longer distances in good light.
- Consider lens size. Choose larger lenses (42mm, 50mm) for brightness and low-light use. Choose smaller lenses (25mm, 32mm) for portability.
- Check the field of view. If you need to scan wide areas or follow fast action, prioritize a wider number (in feet at 1000 yds).
- If you wear glasses, verify the eye relief is 15mm or longer.
- Try them if possible. How they feel in your hands and against your face is just as important as the specs on paper.
Remember, the “best” binoculars are the ones that fit your specific needs and are comfortable enough that you’ll actually use them. Don’t get overly focused on just the highest numbers; balance is key. Now that you know what the numbers mean, you can shop with confidence and find the perfect pair for your adventures.
FAQ: Common Questions About Binocular Numbers
What does 10×50 mean on binoculars?
It means the binoculars have 10x magnification, making objects appear 10 times closer, and have 50mm diameter objective lenses for gathering light, which is great for low-light conditions.
Are 10×42 binoculars good for bird watching?
Yes, 10×42 binoculars are an excellent choice for birdwatching, especially in open areas where you need more detail at greater distances. They offer a good balance of power and light gathering, though the field of view is slightly narrower than an 8x model.
Which is better: 8×42 or 10×42?
It depends on your use. The 8×42 offers a wider field of view, a brighter image (due to a larger exit pupil), and is easier to hold steady. The 10×42 brings you closer for more detail but is slightly shakier in the hand and has a narrower view. For general purpose, many prefer 8×42.
What do the numbers 7×35 mean?
The numbers 7×35 indicate 7x magnification and 35mm objective lenses. This is a classic configuration known for its very wide field of view and ease of use, making it good for scanning landscapes or following fast action.
Is a bigger exit pupil better?
Generally, yes. A bigger exit pupil (like 5mm vs. 2.5mm) provides a brighter image and makes it easier to position your eyes quickly. This is advantageous in low light and for users who wear glasses.
What does “field of view 340ft/1000yds” mean?
It means that when you are looking at something 1000 yards away, you will see a horizontal span of 340 feet wide through the binoculars. A larger number here means you can see a wider area without moving the binoculars.