If you’re looking at binoculars, you’ll see a pair of numbers like 8×42 or 10×50. What do the numbers mean for binoculars? These figures are the key to understanding a binocular’s power and capability. They tell you how much closer things will appear and how well you’ll see in different lighting. Getting to know them is the first step to choosing the perfect pair for your needs.
What Do The Numbers Mean For Binoculars
The two numbers you see, such as 8×42, are the magnification and the objective lens diameter. They are always presented in that order: magnification first, then lens size. Let’s break down each one so you know exactly what your buying.
Magnification (The First Number)
The first number (before the “x”) is the magnification power. It tells you how many times closer the subject will appear compared to your naked eye. An 8x magnification makes an object look eight times closer. A 10x magnification makes it look ten times closer.
- 8x Binoculars: Offer a wider field of view and are generally easier to hold steady. Great for general wildlife viewing, sports events, and scanning landscapes.
- 10x Binoculars: Bring subjects significantly closer, ideal for long-distance observation like birding at a lake or stargazing. They can be harder to hold perfectly still without support.
- 12x and Higher: Provide very high power but almost always require a tripod to avoid shaky images. Used for specialized astronomy or long-range terrestrial spotting.
Objective Lens Diameter (The Second Number)
The second number (after the “x”) is the diameter of the front lenses, measured in millimeters. This is crucial for light gathering. Larger lenses capture more light, resulting in a brighter image, especially in low-light conditions like dawn or dusk.
- 20mm to 25mm (Compact): Small, lightweight, and portable. Image brightness can suffer in poor light.
- 30mm to 36mm (Mid-size): A popular balance of size, weight, and light-gathering ability. Very versatile for daytime use.
- 42mm to 50mm (Full-size): Excellent light collection provides bright, clear images. These are the standard for serious birding and wildlife observation, but they are heavier.
- 50mm and Above (Large): Maximum light gathering for astronomy or marine use. They are often bulky and heavy.
How Magnification and Lens Size Work Together
The combination of these two numbers defines the binocular’s performance. You can’t just look at one in isolation. For example, both an 8×42 and a 10×42 have the same lens size, so they will gather the same amount of light. But the 10x will show you more detail on a distant bird, while the 8x will give you a wider, steadier view.
A key spec derived from these numbers is the exit pupil. You can calculate it by dividing the objective lens diameter by the magnification. For 8×42 binoculars, 42 ÷ 8 = 5.25. The exit pupil is 5.25mm.
- What Exit Pupil Means: This is the small circle of light you see in the eyepiece. It should match or exceed the size of your eye’s pupil in low light (about 5-7mm for a young adult).
- Larger Exit Pupil (e.g., 5mm+): Provides a brighter image and makes it easier to find and keep the view, especially if your hands are shaky.
- Smaller Exit Pupil (e.g., under 3mm): The image may appear dimmer in low light, and eye placement becomes more critical.
Other Important Numbers and Specs
While the two main numbers are most critical, other specifications on the box or body provide further details.
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 (e.g., 400 ft. at 1000 yds.) makes it easier to follow moving subjects like birds or athletes. Higher magnification typically results in a narrower field of view.
Close Focus
This is the minimum distance at which the binoculars can focus. If you enjoy looking at butterflies, insects, or flowers, a close focus of 6 feet or less is very desirable. Some general-purpose binoculars may only focus down to 15 or 20 feet.
Eye Relief
This is the distance from the eyepiece lens to your eye where you can still see the full field of view. It’s vital for eyeglass wearers. Look for a long eye relief (15mm or more) if you wear glasses, so you can see the entire picture without removing them.
Choosing the Right Numbers for Your Activity
Matching the numbers to what you’ll be doing most ensures you’ll be happy with your purchase. Here’s a simple guide:
- General Use & Hiking: 8×32 or 8×42. They offer a great mix of brightness, steady view, and portability.
- Birdwatching: 8×42 is the classic, versatile choice. 10×42 is excellent for open areas and waterfowl.
- Sports & Concerts: 8×25 compacts or 8×32 models are easy to carry and provide a wide, stable view from stadium seats.
- Astronomy: 10×50 or 15×70. Large objective lenses for maximum light gathering, often used with a tripod.
- Marine & Boating: 7×50. The lower magnification is steadier on a moving boat, and the huge 50mm lenses give a bright image.
- Theater & Museums: Low-power compacts like 4×30 or 5×25 are perfect for close quarters and have an extremely wide field of view.
FAQs: Understanding Binocular Numbers
Q: Are higher magnification binoculars always better?
A: Not always. Higher power (like 12x) magnifies hand shake, making the image jittery. It also narrows the field of view and often requires a tripod. For most handheld uses, 8x or 10x is ideal.
Q: What does 10×50 mean on binoculars?
A: It means the binoculars have 10x magnification, making objects appear ten times closer. The 50 refers to the diameter of the front objective lenses in millimeters, which are large for gathering a lot of light.
Q: Which is more important, magnification or lens size?
A: They work as a pair. For bright images in low light, lens size is critical. For seeing fine detail at distance, magnification is key. You need to balance them based on your primary use.
Q: What is the best all-around binocular size?
A: The 8×42 configuration is widely considered the best all-around size. It offers very good light gathering, a steady and wide view, and is still manageable to carry for extended periods.
Q: Can I use binoculars with eyeglasses?
A: Yes, but you must look for models with long eye relief (15mm or more). Many binoculars have twist-down eyecups that allow you to get your eyes closer to the lenses with glasses on.
Q: What does “field of view” mean?
A: It’s the width of the scene you see through the binoculars, measured in feet at 1000 yards. A larger number means you can see a wider area, which is helpful for tracking animals or watching sports.
Final Tips Before You Buy
Now that you know what the numbers mean, your final step is to try them if possible. Visit a store to feel the weight and check the view. Look for a sharp, clear image from edge to edge. Check that the focusing knob turns smoothly. Ensure the binoculars fit comfortably in your hands and that the eyecups suit your eyes, with or without glasses. Remember, the best binoculars for you are the ones with the numbers that match your hobby and feel good to use for a long time. With this knowledge, you can confidently interpret any model’s specifications and find your perfect pair.