Selecting Binoculars

Selecting Binoculars for Birding
Most birders have one pair of binoculars that must serve under a wide range of viewing conditions. Some birders prefer having a larger pair that gathers the maximum amount of light for owling and other low-light situations, and a lighter weight pair for more typical daytime conditions. But most birders take the same pair along no matter what they’re viewing, and so it’s important to select binoculars with all your viewing needs in mind.

How far can you see through binoculars?
If you’re viewing the night sky, you’ll be able to see more stars with binoculars than without. And with binoculars you’ll be able to resolve individual birds in a flock to count them at distances from which you simply couldn’t resolve the individual birds with your eyes. But overall, you’re not going to see farther with binoculars than you can with your own eyes. What you will be able to do is bring birds closer, so you’ll be able to resolve many details you couldn’t see with your naked eye. Binoculars also do something else—they narrow your field of view to help you focus all your attention on one thing at a time. When I’ve been at evening slide programs with other birders who came in after a day of birding, I’ve always been surprised at how many of us automatically pull up our binoculars to better view the details of birds on the screen, even though they’re already huge. This is reflexive—after a while birders simply do this whenever we see a bird without even thinking about it. Why use binoculars when we can see it just fine through our eyes? When we look at anything through binoculars, we don’t see anything outside of the binoculars’ field of view to distract us. This focusing of our attention as well as our eyes becomes second nature.

Every pair of binoculars is described by two numbers, such as 8x42 or 10x50. The first number refers to the magnification. The second number is the diameter (in millimeters) of the objective lens (the larger, front lens).

Magnification
Virtually all birding binoculars are 7x, 8x, or 10x, though a few birders use binoculars up to 15x. There are advantages and disadvantages to each. The higher the magnification, the more detail you see and the bigger the image you’re looking at. Even though the differences are technically significant, in 90 percent of your viewing situations, the power of binoculars won’t make a difference in your ability to find and identify birds.

The smaller your magnification, the more of the scene you will see and, for the same size glasses, the brighter your image. When hawk-counting, 7x binoculars can show a few more hawks in the sky at a given moment than 10x do. Also, when a bird is moving quickly, you have a better chance of actually finding it in the field of view using lower-power glasses. And lower-power binoculars can focus closer than comparable higher-power models.

The higher the magnification, the worse the effects of heat shimmer and any hand shaking. Also, for otherwise comparable binoculars, the higher the magnification, the heavier the binoculars, the harder to focus on close objects, and the more rotations of the focus wheel to go from near to far. Very few advanced birders use 12x or higher because of the small field of view, the difficulty in holding them steady, their low light, and their heavy weight. And very few advanced birders even consider zoom binoculars because the zoom mechanism compromises optical clarity (though not nearly as much as in the past when manufacturers used less advanced coatings). Zoom binoculars are also heavier than comparable standard binoculars. Image stabilized binoculars make up for the shaking and distortion, but are bulkier and weigh more than comparable non-stabilized models.

Birders who also enjoy dragonflies and butterflies often select 7x binoculars for their closer-focusing capabilities. Birders who watch owls, woodcocks, or other birds most often seen in low-light or night conditions also prefer 7x or 8x.

Birders who watch hawks have to balance the extra detail they get from 10x with the larger field of view (which can include more hawks in a single image) seen through 7x.

One other consideration about magnification is that any flaws in the design or optics of a line of binoculars will be increased at higher magnifications. If a focus wheel needs a lot of adjustments on a 7x pair, it will need even more adjustments on a 10x pair. If low power binoculars are not particularly bright, higher power binoculars in that line will be dimmer. I’d never consider 10x binoculars in inexpensive lines—to get the best quality for the money, lower power would definitely be wiser. Of course, to get the most value in any line of binoculars, lower power glasses are virtually always significantly less expensive than higher power glasses of comparable quality.

Because of the tradeoffs, the majority of birders who have just one pair of binoculars prefer 8x binoculars, but there are excellent, advanced birders using each power, even 15x. If you aren't sure which you prefer, try to compare them in the field. You can try out other people's binoculars when you go on field trips, or test various models at vendor displays at birding festivals.

Diameter of Objective Lens
The second number describing binoculars refers to the diameter of the objective lens, measured in millimeters. Pocket or compact binoculars usually have smaller than a 32 mm lens and some are as small as 18 mm. This makes them wonderfully easy to carry around in a purse or pocket. To offset this advantage, they’re uncomfortably small for many hands and don’t work well under low light conditions. You really do need something bigger to see owls, woodcock, or other birds under the lowlight conditions they’re usually seen in.

Binoculars with an objective lens over 50 mm let in enormous quantities of light, an advantage offset by their extra weight. Many birders now use a harness rather than a neck strap, and this is especially helpful with large binoculars.

Most standard binoculars have an objective lens between 35 and 50 mm. Since magnification power also affects how bright your image is, a single line of binoculars tends to have larger objective lenses as the magnification power goes up. The general rule when I started birding in 1975 was that to get decent light-gathering you needed binoculars with a second number at least five times the first number (i.e. 7x35, 8x40, 10x50). But as the quality of lenses and coatings has improved, that rule no longer holds true, especially for high-end and even many mid-price binoculars. But a great many birders believe that the ideal binoculars are 8x40 or 8x42 because of their relative light weight for optimal light gathering capabilities. Indeed, at the time of this writing, the Zeiss 8x42 FL T binoculars had just been given the highest rating of all tested binocular models by the Cornell Laboratory of Ornithology in their Journal, The Living Bird.

Exit Pupil and Optical Quality
The Exit Pupil is a number describing the magnified image in the eyepiece as it leaves the binocular to enter your eye. You can figure out what it is by dividing the size of the objective lens by the magnification power. That is, 10x50 binoculars would have an exit pupil of 5mm, and 7x42 binoculars would have an exit pupil of 6mm. You can judge both the size of the exit pupil and the quality of binocular optics by holding the binoculars at arm's length and looking at the spot of light in the eyepiece. The larger it is, the larger the exit pupil. Exit pupil is one indication of how well you can see at twilight or at night. Brightness of the image is also greatly affected by the quality of the glass and the coatings, but an exit pupil of at least 4mm is important if you ever bird in twilight or shadowy conditions. This is why pocket binoculars aren’t the best choice for low-light birding. 8x40 binoculars have an exit pupil of 5, and 8x42 are even better for superior light gathering.

While looking at the light spot to judge the size of the exit pupil, pay close attention to how crisp it is. The sharper the edges, and the more perfect a circle, the higher quality the optics. To test whether the binoculars are properly aligned, hold them out or, better, set them on something level, pointed at a straight horizontal line such as a shelf, the line between a wall and ceiling, or a distant building. If the binoculars are truly aligned, the line should be at precisely the same level in each of the eyepieces.

Eye Relief
One number that usually isn’t featured conspicuously on binocular specifications but can be very important if you wear eyeglasses is Eye Relief. This is the measurement, in millimeters, of the optimal distance between your eyeball and the ocular lens of the binoculars. Binoculars virtually never have the eye relief written on them, but you can make a rough estimate by simply looking at the eye cups. Manufacturers design their eye cups to hold the binoculars at the right distance from the naked eye. No matter what the eye relief is, if you don’t wear eyeglasses you can extend the eye cups and they’ll be set at the proper distance for you. If you and everyone else who uses your binoculars don't wear eyeglasses, eye relief won't matter at all.

But if you do wear eyeglasses, you want to make sure that the eye relief is about the distance from your eye to the outer surface of your eyeglass lenses. Glasses with thick lenses or frames that hold them well out from your eyes require binoculars with longer eye relief than glasses with thin lenses in frames that are close to your eyes.

How do you figure out what the best eye relief for you is? If you have an opportunity to test out several different binoculars with different eye relief, you can see what the specs are on the binoculars that work best for you. Otherwise, you may simply have to make an educated guess. If you wear small, close-fitting glasses, an eye relief of 14 or 15 should be right. If your glasses are thicker and/or farther fitting, try 16-18.

Even if the eye relief doesn’t properly match your glasses, you’ll still be able to see through binoculars. But when the eye relief is shorter than it should be, your field of view will be narrower and the image will not be as large as it would be with proper eye relief--this is often called "tunneling" or "tunnel vision." If the eye relief is longer than it should be, you may find yourself holding the binoculars slightly out from your glasses, making them harder to hold steady. Fortunately, more and more binoculars are coming with adjustable eyecups, allowing you to extend them slightly if necessary to hold them at the perfect distance from your eyes.

Price and Warranty
In general, with binoculars as with so much else, you get what you pay for. But there are important considerations to keep in mind when comparing prices. First, between the least expensive binoculars (less than, say, $60) and mid-price binoculars (say, between $200 and $500) there is an enormous jump in quality. Top of the line glasses ($1000 +) are almost without exception superior to all others, but the jump in noticeable quality may not be as huge as the jump in price. Hawk counters, researchers doing field surveys, and other people who use binoculars for many, many hours a week will benefit from the improved optics of high-end over mid-range binoculars, but for most users this difference isn’t as critical, and they really do often get their best value with mid-range or "top affordable" ($500 - $1000) binoculars. Of course, there is often an eye-popping gasp when someone first looks through the newest top line optics, which really are amazing.

In addition to price, the length and conditions of the warranty help determine the best value. A few manufacturers offer “no questions asked” warranties which cover binoculars that fall off car hoods, get dropped into saltwater, or fall victim to other birding hazards. The more you spend on binoculars, the more important the terms of the warranty are.

Binocular design

At the same price point, the optics in porroprism binoculars are simpler and so usually higher quality than roof prism binoculars, so in lower price lines, porroprisms are sometimes the wiser choice. They tend to have good light gathering and depth of field, though they’re heavier, bulkier, and have an external focus, making them more vulnerable to water and dirt damage.

Remember that the more you spend on binoculars relative to what you can comfortably afford, the more protective of them you’ll be and the more reluctant to bring them canoeing or biking. You’d see way more birds through more affordable binoculars you’re comfortable bringing everywhere than you’ll see through the finest quality optics that you leave at home. But also remember that inexpensive binoculars may not be as durable. When binoculars are knocked out of alignment, they can cause eye fatigue and headaches, especially if you use them for long periods.

Depth of Field
Binoculars that are “auto-focusing” maximize the depth of field, meaning you are constantly focused on both near and far. The trade-off is that visual acuity at every distance is sacrificed. A precise focus adjustment is far better for getting the level of clarity that birders need. But for birding, you also want to be able to switch almost instantly from a nearby hummingbird to a distant hawk. The more turns on a focusing knob you must make to switch from near to far (or vice versa), the more birds you’ll miss. And the more focusing adjustments you need to make to keep a single warbler in view as it flits from branch to branch, the more frustrated you’ll get. When comparing binoculars, see how many pushes you need to give the focusing knob to go from near to far with each model, and see how easy it is to stay focused on a moving bird.

Field of View
Field of view is given either as the width of your view at 1000 feet, or as a number of degrees. Wide angle binoculars give you a wider field of view, making it easier to locate birds when you’re inexperienced at using binoculars, but unless the binoculars are expensive, the added field of view is often blurry. Wide angle binoculars are heavier than comparable standard ones, and sometimes not quite as crisp. Most birders prefer standard binoculars unless they do a lot of work counting birds in the sky. Even when I was counting flocks of migrant songbirds and hawks at Hawk Ridge Nature Reserve, I found my standard binoculars perfectly satisfactory.

Close Focus
Many birders are now also looking at butterflies and dragonflies, which are often only a few feet away, and so “close focusing” binoculars have become very popular. But close-focusing within a few feet comes at the cost of some optical clarity and having to make more corrections with the focus knob to keep things in focus. If you want this feature, make sure to test how easily you can switch from looking at something close to something far. You don’t want to miss a Peregrine Falcon flying along the horizon just because you were enjoying a beautiful Blue Darner.

Added features

• General “Feel” and Portability: When buying birding binoculars, you want to make sure they feel good in your hands. For a while I switched to a high-end pair of binoculars with exceptional optical clarity, but simply could not adjust to how heavy and large they were in my hands. My mother-in-law has a pair of pocket binoculars that she’s used constantly for 15 years and loves for their portability—she often puts them in her purse just in case she comes upon an interesting bird. But my father-in-law hated them because they were just too small for his hands. If your binoculars aren’t a convenient and comfortable size, they’re not going to be used, and simply won’t give you the value you’re paying for.
  
• Coatings: Don’t even consider binoculars that aren’t “fully coated.”
  
• Focus Adjustment: Make sure that the focus adjustment is in a convenient place for your hands, to make focusing simple and fast. For birding, don’t even consider binoculars without a central focus—it’s simply too hard to keep birds in focus when you have to constantly adjust the eyepieces separately. Fortunately, virtually any binoculars marketed for birders have a central focus.
  
• Eyecups. When I started out birding in 1975, just about every pair of binoculars available had rubber eye cups. These were perfectly suitable for people who always wore eyeglasses, or for people who never wore glasses but shared binoculars with people who did. But I sometimes wore contacts lenses and sometimes wore eyeglasses. When I wore contacts, I’d have to pull the rubber eye cups out. When I put on my glasses, I had to push the eye cups down. This frequent bending and straightening quickly cracked the rubber. The eye cups broke off of two different pairs of binoculars—one a very inexpensive model, the other mid-range pocket binoculars—each within a year. My first pair of top-line binoculars also had rubber eye cups, but these were much sturdier. Although they have developed very shallow cracks, they’re still working well after 15 years, though rolling them up and down is rather a nuisance.

  One of the most practical little innovations in recent years has been telescoping eye cups. Rather than rolling rubber eye cups up and down, these pull out and push in or twist in and out. Some have definite stop-points that allow fine-tuning so they work well with different kinds of eyeglasses. Telescoping eye cups are far sturdier and far easier to use than the old-fashioned rubber eye cups and aren’t very expensive to manufacture, so most companies have switched to them even on their least expensive lines. If you will need to open or close the eye cups occasionally, and especially if you need to change them frequently because you only wear eyeglasses sometimes or share your binoculars with someone, make sure to get binoculars with telescoping eye cups. Ones with a screwing mechanism are usually more satisfactory than those that simply push in and out.

• Neck Strap or Harness? The quality of the neck strap on a pair of binoculars becomes increasingly important the more you wear your binoculars, and the hotter or more humid your surroundings. Some things to consider:
  
  • Try to avoid pocket binoculars with a string rather than a strap if you plan on wearing them around your neck for any length of time.
  • A harness can be wonderfully comfortable, but makes the binoculars hard to pass off to others. Neck straps make sharing binoculars far easier.
  • Harnesses can be awkward to get on and off when you start off the day in a jacket which you’re going to shed. They’re also hard to use over thick down jackets.
  • Despite their drawbacks in those cases, binocular harnesses are a wonderful innovation for alleviating neck strain and being comfortable wearing binoculars for many hours at a time.
  • Because of the different advantages of both, many birders switch back and forth depending on their needs on a given day. If you think you’ll do this, make sure you select a strap and a harness that are easy to take off and put back on the binoculars.
    
    
• Image stabilizer? The higher the magnification of your binoculars, the harder they are to hold steady. New birders often have an unsteady hand, and for most it’s simplest to start out with 7x or 8x binoculars—practice will improve your skills and you may be able to move up to 10x’s if you like.
  
  A shaking image can be a real problem in cold temperatures when you’re shivering, and if you suffer from any kind of tremors, holding standard binoculars steady can be very hard. If you frequently use binoculars in a moving car (hopefully you’re the passenger!), on rope bridges, or on other unsteady surfaces, image stabilizing can be a wonderful feature.
  
  For otherwise comparable optical quality, binoculars with image stabilizing cost significantly more than standard binoculars and are bulkier and heavier. They also tend to have poorer light gathering, even at lower powers. They’re certainly worth considering if you frequently bird on unstable surfaces or in frigid temps, or if you suffer from any kind of tremors.
  
  
• ED lenses? Some high-end binoculars now sport “ED” lenses The ED stands for Extra-low Dispersion. When light travels through a glass lens, the three primary wavelengths of light (red, green, and blue) do not come to focus at the same point in the optical system. Due to variations in the wavelength of each color of light, each color will travel through the glass lens at a slightly different angle, resulting in a colored haze around objects viewed through the glass.
  
  In a very basic pair of binoculars, multiple glass elements are used to combat the resulting color fringe, or haze, which occurs from these different focal points. By using one convex lens and one concave lens, the red and blue spectrums can be brought to focus at a point closer to where the green light comes to focus. The addition of the second lens reduces the size of the haze seen around objects and causes the image to appear more in focus. This simple arrangement is called an achromatic system.
  
  In order to eliminate even more of the color fringe, different types of glass are used which will allow the focal points of each of the colors of light to be brought closer together. In these apochromatic systems, the light is corrected for the wavelengths in between the primary colors, as well. The resulting focal points reduce the extent of the color fringe and allow edges to be seen more clearly. Extra-low dispersion glass (such as fluorite) is used to equalize the focal points across the color spectrum and provides a crisper image than achromatic or uncorrected systems.
  
  So ED glass is unsurpassed at providing crisp images. But it’s more expensive and more difficult to manufacture, making binoculars with it significantly more expensive than otherwise comparable ones. So most companies offer only select models with ED lenses. Typically, ED lenses are used only on a manufacturer’s premiere model and coated with some of the best optical coatings available.
  
  
• Intangibles: After you’ve seen the sun sparkling on your first Ruby-throated Hummingbird, or a Great Gray Owl staring right through your binoculars into your eyes, those binoculars are going to seem pretty darned perfect. Perhaps that’s why so many birders show such very strong brand loyalty. I keep a “Zeiss List”—that is, a list of all the birds I’ve seen through my Zeisses. That Zorro-like “Z” marking each species is a cool little thing for me, but absolutely meaningless for others—it’s also why I’d be reluctant to buy another brand, for which I’d have to change the symbol and start all over. I bought a Kowa scope in 1996 in part because I’d been fixated on the brand for years after seeing some wonderful birds through a friend’s, and noticed that any time I saw a new bird through that scope, I could yell out “Kowa-bunga!” This is the kind of intangible bonus that a birder with one kind of sense of humor delights in while another finds it downright stupid. The truth is, whether you’re looking at top-tier, mid-range, or economy binoculars, there will be different models that are very comparable in quality. Some of these little intangibles may influence your choice. And that’s perfectly okay.

So, after all that, how do I choose a pair of binoculars?
Know how much you can afford before looking at binoculars. Top line binoculars really are brighter and crisper than less expensive models, and if you can’t afford them, don’t open yourself up to dissatisfaction with what you can afford. That said, remember that a good pair of binoculars can last for many decades, and if you use them often, you really will value the superior quality of top line optics. I spent my family’s entire discretionary income for 1989 on a pair of Zeiss 10x40 BGAT’s that, 16 years later, are still extremely satisfactory. But if you are considering buying binoculars that are more expensive than you can comfortably afford, take into account whether you’re going to treat them delicately and leave them home sometimes, missing good birds. Better to buy in your price range and use them wherever you go. If you do need to economize, it’s virtually always a better value to buy lower power than higher power, and to get a standard rather than a wide angle view. 7x or 8x in a higher quality binocular will virtually always provide a far more satisfactory image than 10x in a lower quality binocular, and may turn out to be not much more expensive.

Compare various pairs that are in your price range with the magnification power you want. First look at the spot of light, and eliminate any choices that have shady or blurry edges, or that are out of alignment. Compare them for the brightness and clarity of the image, how comfortable they are in your hand, and how heavy they are. If you wear eyeglasses, compare different pairs of binoculars. Don’t take off your glasses! You’ll miss too many birds if you get into the habit of taking off your glasses to use your binocs. If you wear glasses, specifically compare various pairs of binoculars to find the ones that are easiest to use with your glasses.

Whether you prefer a neck strap or a harness, make sure it can be removed and replaced in the event that it gets broken or you find a more comfortable one. Binoculars with strings permanently affixed are not a good choice for birding!

Make sure the binoculars feel good and provide you with good clear views. Look at real, live birds through them if at all possible before making a final decision. See how easy it is to find birds and keep them in view when they’re moving. And if you buy from a company like Binoculars.com with a 7-day return policy, get out there and test the binoculars on real live birds for those 7 days. It’s far more fun for most birders to focus attention on birding than optics. So make sure you’re satisfied, and then forget about optics and go birding!

~ Laura Erickson