Model numbers on binoculars essentially tell you their strength (magnification power) and size (objective lens diameter). In 8×42 binoculars, for example, “8” is the magnification power and “42” is the diameter (in millimeters) of the objective lenses (the lenses closest to the object you’re viewing). Objective lens size gives you an understanding of how physically big the binoculars are and how much light they can gather. When you understand what these numbers mean and how they affect your viewing, you’ll know if you’re choosing binoculars that will be good for birding, stargazing, or using on a moving boat, for example.
Magnification and Objective Lens
All binoculars are identified by a set of numbers, such as 10×42 and 7×20, which refer to their magnification and objective lens diameter, respectively. Using 10×42 as an example, the 10x means that the binoculars have 10x magnification power, making the view through them appear 10 times closer than it appears to the naked eye. For most situations, users should look for binoculars from 7x to 10x power. Theatergoers should choose something in the range of 3-5x, depending on your seats; sports fans will be happy with a 7x model; while big-game hunters would need 10x or higher for long-range observations. Keep in mind that for many users, holding binoculars greater than 10×42 steady for long periods may present some difficulty, so a tripod should be considered if you are looking at models with higher magnifications or larger objectives.
The objective lenses of binoculars are the front lenses. The diameter of the lens determines how much light enters the binocular’s optical system, translating into greater detail and image clarity. The greater the objective lens size, the more detail you will see. Larger objective lenses also make the binoculars themselves larger and heavier. You’ll want to find a balance between brightness and portability that works for you. A 42mm objective lens is generally considered to be full-sized. This has become the standard for bird watching and wildlife viewing. At this diameter, you’ll generally be able to make out subtle color differences in birds, even when it’s overcast, early in the morning, or late in the day.
Field of View and Eye Relief
Field of view is the width of the area visible when you look through your binoculars – a critical factor to consider when selecting the right pair for your needs. Real field of view is the angle of the visible field, seen without moving the binoculars, measured from the central point of the objective lens. The larger the value is, the wider the viewfield you obtain. For example, binoculars with a wider field of view are advantageous for locating fast-moving wild birds within the viewfield. This also applies for finding small nebulas or a cluster of stars in astronomical observations.
Eye relief is the distance at which the binoculars can be held away from the eyes and still provide a full field of view. High-eyepoint binoculars with eye relief of 15mm or longer are recommended for eyeglass wearers. Choose binoculars with eye relief of at least 10mm. The eyepiece lenses should rest an appropriate distance from your eyes, and even further if you wear glasses. This is called “eye relief” and normally ranges from 5–20 millimetres (0.20–0.79 in). If you wear glasses, you’ll need an eye relief of 14–15 millimetres (0.55–0.59 in) or greater, as most eyeglasses rest from 9–13 millimetres (0.35–0.51 in) from the eye.
Choosing Binoculars for Specific Activities
Bird Watching
For bird watching, go for 8-power magnification so that you get a wider field of view. The standard binocular for birding is an 8×42 binocular. To see more details on smaller birds at greater distances, you may opt for a 10×42 to a 12×50. Longer eye relief and a close focus are also great features to have on your bird-watching binoculars. Prioritize larger lenses for bird watching or low-light activities. Binoculars with larger objective lenses have wider fields of view, which are better for finding and following birds when you’re bird watching. Larger lenses are also able to gather more light, which is important in low-light activities like night hunting.
- Choose 8×42 or 10×42 for versatility and brightness.
- Ensure a wide field of view for tracking fast-moving birds.
- Look for binoculars with at least 15mm eye relief if you wear glasses.
Stargazing
Here’s where you want to maximize magnification as well as the light gathering ability of full-size binoculars. 10×42 or 10×50 are options to consider; if you go with higher magnification, you’ll need a tripod to hold the binoculars steady. For astronomy and stargazing, get a pair with large objective lenses (70mm is common) and low magnification so you can see vast, dim objects like nebulae and galaxies. Larger objective lens diameter – ideally around 42mm or 50mm – gathers more light, making them suitable for stargazing in darker environments where you need to see faint celestial objects.
- Opt for 10×50 or larger for better light gathering.
- Use a tripod for magnifications above 10x to reduce shake.
- Choose multi-coated lenses to reduce glare and improve clarity.
Hunting
For hunting, the best type of binoculars range from 7×18 to 10×56. For long-range shooting, such as varmint hunting, more powerful binoculars like 12×40 to 16×50 are best. At larger magnification, you will need to use a tripod to stabilize the binoculars, as the image will be very shaky if used in a standing position. Generally speaking, if you’re hunting in dense, tighter habitats, you’ll benefit more from an optic with less magnification and a greater field of view – approximately 340ft or greater (ft/1000 yds).
- Select 8×40 or 10×50 for a balance of clarity and portability.
- Choose durable, waterproof models for rugged conditions.
- Consider a tripod for long-range observations.
Sports and Concerts
Choosing a pair of binoculars for sporting events and concerts is a matter of balancing width and depth in your field of vision. Compact and wide-angle binoculars are great for outdoor activities and getting closer to the action watching sporting events at the stadium. Compact binoculars are usually found at 7×25 to 10×50 ranges. This style is easy to store in your pocket or on a strap around your neck, letting you bring them with you without worrying about taking up too much space.
- Go for compact 7×25 or 8×30 models for portability.
- Ensure a wide field of view to follow fast action.
- Look for lightweight designs for extended use.
Key Features to Look for in Binoculars
Lens Quality and Coatings
The type and quality of the glass used for the lenses and prisms matter. Generic optical glass may have imperfections, and if it isn’t ground and polished correctly, it could bend light oddly, causing colors to look skewed or prevent its ability to achieve tack-sharp focusing, or you may notice distortion at the edges. Specialized glass, such as low dispersion or extra low dispersion, is engineered to have virtually no distortion and transmit light better without bending it. The resulting images are generally clearer, sharper, with true color rendition and higher contrast. You may also see some binoculars made with “Eco-glass.” This general term refers to ecologically friendly glass that doesn’t use lead or arsenic.
Optical coatings, such as anti-reflective coatings, improve light transmission and reduce glare. They’re applied to lens surfaces to enhance contrast and clarity by minimising reflections that can cause image degradation. Multi-coated lenses, for example, have multiple layers of coatings that further enhance the amount of light efficiency, resulting in brighter and clearer images even in low-light conditions. With a good coating, you get crisper and brighter images with clear contrasts. In uncoated lenses, around 4% of incident light per lens or air transition gets reflected.
Prism Type: Porro vs. Roof
There are two main types of prisms used in binoculars: Porro prisms and roof prisms. When you look at porro binoculars from the side, their eye pieces (oculars) are offset from the position of the lenses (objective lenses) at the front of the binoculars. In comparison, the barrels of roof prism binoculars are straight. When a pair of porro binoculars are focused, the eye pieces move back and forth. However, when focusing a pair of roof prism binoculars, the eye pieces remain stationary. Generally speaking, porro binoculars weigh more than roof prism binoculars. Also, roof prism binoculars sometimes have a tendency to be jarred out of alignment more easily than porro prism models.
| Feature | Porro Prism | Roof Prism |
|---|---|---|
| Design | Offset eyepieces, bulkier | Straight barrels, sleeker |
| Weight | Heavier | Lighter |
| Durability | More robust alignment | May need realignment |
| Cost | Generally cheaper | Often more expensive |
Weatherproofing and Durability
There are two types of designations commonly used when talking about weatherproofing. The differences are: a weather-resistant optic will withstand the occasional light shower but will not withstand submersion or extended use in wet conditions. Weatherproof or waterproof optics means that the optics shouldn’t allow water intrusion under most circumstances. Sometimes they are even rated to a depth of submersion for a period of time. Rubber armoring provides a final level of external ruggedness and helps protect your binoculars from abrasion, damage, or loss of collimation if accidentally dropped. The rubber also makes them easier to grip in damp or wet weather conditions.
How to Test Binoculars Before Buying
The best way to evaluate the optical performance and ease of use for a pair of binoculars is to go to a store and look through several before you make a final choice. To get a sense of focusing ease, how comfortable binoculars feel in your hands and their optical clarity and brightness, you need to visit a store where you can try out several of the models you’re considering. If the retailer doesn’t have a test chart to view, then focus on a detailed object across the store. Pay close attention to the overall sharpness and brightness of the image, as well as the consistency of clarity and brightness from side to side in your field of view.
- Test the focusing function by calibrating on a nearby object.
- Check image quality for sharpness and color accuracy.
- Ensure the eyecups are comfortable, especially if you wear glasses.
- Evaluate weight and balance for extended use.
Best Binoculars Recommendations
Here are some top picks for binoculars based on specific needs, available on Amazon with affiliate links for easy purchase.
| Model | Best For | Specifications | Link |
|---|---|---|---|
| Celestron Nature DX ED 12×50 | All-around use | 12x magnification, 50mm objective lens, multi-coated | Buy on Amazon |
| Nikon Prostaff P3 8×42 | Beginners, birding | 8x magnification, 42mm objective lens, waterproof | Buy on Amazon |
| Canon 10x42L IS WP | Long-distance, stargazing | 10x magnification, 42mm objective lens, image stabilization | Buy on Amazon |
For more detailed reviews, check out Audubon’s Binocular Guide or Cornell Lab’s Testing Tips.
Frequently Asked Questions
What do the numbers on binoculars mean?
The numbers, like 8×42, indicate the magnification (8x) and the objective lens diameter (42mm). Higher magnification brings objects closer, while larger lenses gather more light for brighter images.
Are expensive binoculars worth it?
Expensive binoculars often use superior glass and coatings, offering sharper, brighter images and better durability. For casual use, mid-range models like the Nikon Prostaff P3 can be excellent, but serious birders or astronomers may benefit from premium brands like Swarovski.
How do I clean my binoculars?
Use a soft, lint-free cloth and lens cleaning solution. Gently wipe the lenses in a circular motion, avoiding abrasive materials like paper towels. Never touch lenses with your fingers to prevent oil smudges.
Can I use binoculars with glasses?
Yes, choose binoculars with eye relief of 15mm or more. Adjustable eyecups allow you to maintain a full field of view while wearing glasses.
What’s the difference between Porro and roof prism binoculars?
Porro prisms have offset eyepieces, are bulkier, and often cheaper, with robust alignment. Roof prisms are sleeker, lighter, but may be pricier and less durable in alignment.