If you’ve ever looked at a pair of binoculars, you’ve seen the numbers printed on them. What does the numbers mean on binoculars? Those figures are the key to understanding the binoculars’ power and capabilities, and learning to read them is the first step to choosing the right pair.
This guide will explain those numbers in simple terms. You’ll learn how to interpret them and use that knowledge to pick the perfect binoculars for birdwatching, sports, or astronomy.
What Does The Numbers Mean On Binoculars
The most common numbers you’ll see look something like “8×42” or “10×50.” This is the binoculars’ specification, and it tells you two critical things: its magnification power and the size of its objective lenses. The first number is always the magnification, and the second is the lens diameter in millimeters.
Let’s break down what each part means for your viewing experience.
Understanding Magnification (The First Number)
The number before the “x” is the magnification. For example, in 8×42 binoculars, the “8x” means objects appear eight times closer than they do with your naked eye. A bird 80 feet away will look like it’s only 10 feet away.
Higher magnification isn’t always better. Here’s why:
- Image Stability: Higher power (like 12x or more) magnifies every tiny hand shake. You’ll likely need a tripod for a steady view.
- Field of View: Higher magnification usually means a narrower field of view. It’s harder to locate and track moving objects like birds or athletes.
- Brightness: Very high magnification can sometimes dim the image if the second number isn’t also large.
For general use, magnifications of 8x or 10x are often the most versatile and easy to hold steady.
Understanding Lens Diameter (The Second Number)
The number after the “x” is the diameter of the objective lenses in millimeters. These are the large lenses at the front of the binoculars. In 8×42 binoculars, each objective lens is 42mm across.
This size is crucial because it determines how much light the binoculars can gather. More light means a brighter, clearer image, especially in low-light conditions like dawn, dusk, or in a forest.
- Small (20-32mm): Compact and lightweight, but may compromise brightness.
- Medium (42mm): The best balance of light gathering and portability. Great for all-around use.
- Large (50mm+): Excellent for low-light (astronomy, wildlife at dusk), but they are heavier and bulkier.
Other Important Numbers and Specs
Beyond the main two numbers, you might see other figures on the body or in the specifications.
Field of View
This is often expressed as a number of feet at 1,000 yards (e.g., 393 ft/1000yds) or as an angle in degrees. It tells you the width of the area you can see through the binoculars. A wider field of view is great for scanning landscapes or following fast action.
Exit Pupil
You can calculate this yourself: divide the lens diameter by the magnification. For 8×42 binoculars, 42 ÷ 8 = 5.25. The exit pupil is 5.25mm. This is the tiny circle of light you see in the eyepiece. A larger exit pupil (over 4mm) provides a brighter image and is easier on your eyes, which is helpful in low light.
Close Focus
This is the minimum distance at which the binoculars can focus. If you enjoy looking at butterflies, flowers, or insects, a close focus of 6 feet or less is very desirable. Some general-purpose binoculars only focus down to 15 or 20 feet.
How to Choose Based on Your Activity
Now that you know what the numbers mean, here’s how to apply that knowledge.
For Birdwatching and Wildlife
- Recommended: 8×42 or 10×42.
- Why: The 42mm lens offers good light for wooded areas. 8x gives a wider, steadier view for tracking, while 10x brings animals slightly closer at the cost of some stability.
For Sports and Concerts
- Recommended: 8×32 or 8×42.
- Why: A wide field of view is key for following the play. You often use them in decent light, so a 32mm lens can keep things lighter. Image stability is also important from the stands.
For Astronomy and Low-Light Use
- Recommended: 10×50 or higher.
- Why: Large 50mm lenses gather maximum starlight. A tripod is highly recommended for magnifications over 10x to counter shake during long viewing sessions.
For Hiking and General Use
- Recommended: 8×25, 8×32, or 10×32.
- Why: Compact size and lower weight are priorities. The 8×32 is a superb compromise, offering a bright enough image without being a burden in your pack.
Putting It All Together: A Simple Checklist
Use this list when you’re shopping or comparing models online:
- Identify the main numbers (e.g., 8×42).
- Decide on magnification: 8x for wider view and stability, 10x for more detail at distance.
- Choose lens size: 32mm for portability, 42mm for all-round performance, 50mm+ for low light.
- Check the field of view if you need a wide perspective.
- Consider close focus if you look at nearby objects.
- Calculate the exit pupil (lens ÷ mag) to gauge low-light performance.
- Finally, try them if you can. Comfort in your hands and at your eyes is very important.
Frequently Asked Questions (FAQ)
What do the numbers 10×50 mean on binoculars?
It means the binoculars have 10x magnification and 50mm diameter objective lenses. They make objects appear 10 times closer and are excellent for low-light conditions due to their large light-gathering lenses.
Are 10×42 binoculars better than 8×42?
Not necessarily “better,” but different. 10×42 brings subjects closer but has a narrower field of view and shows more hand shake. 8×42 offers a wider, steadier view. The best choice depends on your primary use and ability to hold them steady.
What is a good field of view for binoculars?
For most purposes, a field of view over 330 feet at 1000 yards is considered good. Over 400 feet is excellent for scanning and tracking. Wider fields are common in lower-magnification models like 8x binoculars.
How does lens size affect binocular performance?
Larger objective lenses (the second number) gather more light, resulting in a brighter image. This is critical in dim conditions. However, they also make the binoculars larger, heavier, and often more expensive.
Can I use high-magnification binoculars without a tripod?
It’s challenging. Binoculars above 10x magnification greatly amplify hand movements, making the image shaky. For prolonged viewing with 12x or 15x binoculars, a tripod or image-stabilized models are almost essential for a clear view.
Understanding the numbers on binoculars takes the guesswork out of shopping. You can now confidently match the specifications to your favorite activities. Remember the balance: magnification brings things closer, lens size affects brightness and weight, and your personal comfort is key. With this knowledge, your next pair will be a perfect fit for your adventures.