Why Binoculars Matter and How to Choose the Right Pair for You

Magnification is expressed as a multiple – e.g., 7x, 8x, 9x. This multiple describes how much larger – or closer – the binoculars make the object you’re looking at appear. It’s the first number you’ll see in basic binocular specifications. Before jumping to the conclusion that bigger is better, keep in mind that as you magnify, you lose peripheral vision and with it, context. In addition, images tend to be shakier at higher magnification.

The objective lens is the large lens at the far end of your binoculars, as opposed to the eyepiece you look through. It’s measured in millimeters. Typical binoculars range from an objective lens of 25mm for the smallest pairs, to 35 or 42mm for more standard sizes, and up to 50mm for the heftiest options. The wider the objective lens, the more light the binoculars let in, making for brighter images. That’s why smaller binoculars (32mm and less) present steeper trade-offs between price and quality than full-size models; getting clear, bright images with a smaller objective lens requires higher-end optics.

The size of the objective lens is the second number in basic binocular specifications, after magnification. For example, you’ll find binoculars described as 7x25, 8x42, and so on.

Field of view is a common source of frustration for binocular users. Bringing distant objects closer makes it harder to see the forest for the trees – or the bird for the leaves. Field of view, often abbreviated FOV, doesn’t figure as prominently in binocular specifications as magnification and objective lens size, but can be found in manufacturers’ product descriptions. Sometimes it’s given in degrees, describing the angle of the magnified field as you look through the binoculars. A bit more intuitively, it can also be expressed as the width of your view in feet at 1,000 yards distance. The typical range for binoculars used by birders is from 5.5⁰ to 8.5⁰, which equates to 290-470 feet at 1,000 yards.

Optics quality can finesse the tradeoffs between magnification, field of view, brightness and size/weight. It also drives the big differences in binocular pricing. Different binoculars use different prisms, different types of glass, and different glass coatings. The best way to get a sense of what these differences mean for you is to read product reviews or, even better, try out a few pairs. At the same time, knowing just a bit of optics lingo can demystify the process. Here’s a primer.

Prisms bend light to invert the images you see through your lenses so that they’re right-side up and correctly oriented. Those binoculars passed down from your grandfather, shaped like a giant “W” and weighing enough to double as a doorstop? They contain Porro prisms, an older technology that bends light in a “Z” shape. While Porro prism binoculars are still in use, offering clarity and a broad field of view at a relatively low price, they tend to be heavy and, despite their bulk, fragile and vulnerable to moisture. Most birding binoculars today use roof prisms, which reflect light in a straight line and give binoculars a more streamlined profile.

The type of glass used in binocular lenses affects the images you see through them. Extra-low dispersion (ED) glass, for example, helps reduce color distortion, particularly in challenging light conditions. Once limited to high-end binoculars, it is now commonly used in mid-range models. High-index glass bends light more efficiently, a property that is particularly important in compact binoculars because of their smaller objective lenses. Fluorite glass occupies the very top end. It provides exceptional clarity and color, but at a premium price.

Glass coatings for lenses and prisms provide a variety of performance enhancements. This includes different levels of anti-reflection lens coating to reduce glare and improve brightness; phase correction coatings to fix the distortions that can arise from subtle misalignments in roof prisms; and dielectric coatings applied to the prisms of high-end binoculars to further sharpen their images. Still other coatings target moisture, dirt and scratches – leading directly to our next topic.

Weather resistance and durability are important if you plan to use your binoculars in less-than-ideal conditions. Hopefully, you won’t drop them in a lake (though some models can survive submersion to a depth of several meters), but if you go birding in different environments, you’re likely to run into rainstorms, freezing drizzle, salt spray, blowing dust and sand, and other challenges to the integrity of your optical equipment. You may also find that despite your best efforts to coddle them, your binoculars suffer the occasional hard knock. Various technologies, from glass coatings to special seals to pressurized nitrogen to rubber armoring, can protect the delicate interior of modern binoculars from outside elements and general abuse. If durability is a particular worry, many mid-range and high-end binoculars come with lifetime repair/replacement warranties. 

Ergonomics and ease of use have various dimensions. Weight tends to be the first to come to mind, perhaps because it’s the easiest to quantify. Comfortable straps or harnesses can lighten the burden, but if your binoculars leave you with a sore neck or are just too cumbersome to carry around, then they’re not the right binoculars for you. In general, you want binoculars that feel at home in your hands, that you can focus quickly and easily, and that can be adjusted to fit the size and shape of your face.

Eye relief is the distance between your eyes and the eyepiece where you can see a full, unobstructed view. Adjustable eye cups will help you get this right, and eyeglass wearers should twist their eyecups down to reduce the distance, while those without eyeglasses will twist them out to extend it. And whether or not you wear glasses, odds are your vision differs slightly between your two eyes. A diopter adjustment mechanism lets you fine-tune the focus of your binoculars to compensate for this. Diopter adjustment is pretty much universal on binoculars in the $200 and up range, but less expensive pairs may either lack it altogether or have just a rudimentary version.

To give a sense of what all this means in practice, Bird Collective co-founders Angie Co and Tina Alleva offer their own experiences when choosing their binoculars. When Angie bought her Zeiss Victory 8x32s, she treated the purchase as an investment; these are the binoculars she’ll use for the rest of her life. She opted for the compact pair after discovering just how much weight the company’s high-end glass adds to their 8x42s compared to her previous Nikon Monarch 8x42s. While the full-size Zeiss binoculars were too heavy for Angie, the compact pair feels perfect.

Tina has also upgraded to Zeiss – in her case, from the starter pair of Nikon Aculons she picked up for $75 when she was a novice and unsure how much she wanted to invest in her new hobby. She believes that starting with the Aculons made her a better birder, forcing her to develop her knowledge and discernment. In fact, one of her first reactions to birding with Zeiss equipment was, “now I don’t have to work so hard!”

Both Angie and Tina advocate trying before buying, having experienced first-hand the idiosyncratic ways individuals and binoculars interact. Tina, testing the Nikon Monarchs that many of her friends swear by, encountered a dark eclipse at the edge of her field of view that no adjustment could eliminate. Angie finds that some models simply don’t fit the shape of her face. And while her husband owns multiple pairs of binoculars, including Zeiss Victory 8x42s (the model that was too heavy for her), when he’s on the go he often reaches for the Vortex Diamondback 10x42s he purchased second-hand from a friend, who had declared them unusable because of their limited field of view. He enjoys the larger magnification and is more comfortable toting this pair around town, given their lower price point and excellent warranty.