Out My Backdoor: Choosing the Right Binoculars

Binocular types (Terry W. Johnson)

By Terry W. Johnson

Beyond a shadow of a doubt, the one piece of equipment that can have the greatest impact on your enjoyment of your backyard neighbors is a fine pair of binoculars.

Since all binoculars look pretty much the same, it is easy to assume that they all perform in a similar manner. The truth of the matter is that such is not the case.

I learned that lesson many years ago. For years, I carried a pair of binoculars that I bought for something like $29.95. I took them hunting, wildlife watching, on vacations and even on my college ornithology field trips. As far as I was concerned the images I saw through them were as good as I could expect.

That long-held belief was shattered when I took a college course in ornithology. On our first field trip I discovered that the quality of my binoculars was quite different than those used by the professor leading the trip.

The outing took place during the spring warbler migration. On this particular morning, small colorful warblers were flitting through the treetops. When I told the professor I was having trouble spotting birds' field marks in the dim, early morning light, the professor said, “Let me take a look at your binoculars.”

When he peered through them a subtle smile flashed across his face as he said, “Son, try mine.”

When I gazed at the birds through his binoculars I exclaimed, “Wow! I can’t believe it!” Through his well-crafted binoculars the birds appeared brighter, clearer and three-dimensional.

If you aren’t satisfied with your current binoculars, or you are going to buy your first pair, here are a few tips that will help you choose the pair that is just right for your needs.

The first thing that you will notice when you step up to the counter is that binoculars come in two forms, porro and roof prism. 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.

While both types perform exceptionally well, some folks will tell you that subjects viewed through porro prism binoculars seem more three dimensional than those viewed through roof prism binoculars. I use both and am very happy with what I see through both of them.

When you begin looking for a pair of binoculars one of the first things you need to decide is what power will best fits your needs. The optics come in a variety of magnifications such as 7x, 7.5x, 8x and 10x. These numbers refer to how many times an image is magnified by the binoculars. For example, an 8x binocular magnifies the deer or bird you are looking at eight times.

For most uses, 7x to 10x binoculars work just fine. Keep in mind that the more powerful the binoculars the more difficult it is to hold them steady. For that reason, many folks, particularly as they grow older, shy away from 10x binoculars.

Every pair of binoculars is stamped with a number that will read something like 8x42, 7x35 and so on. The first number tells you the power of the binoculars and the second number refers to the diameter of the lenses (objective) mounted at the front of the instrument. The larger the second number, the larger the objective lens. In other words, 50 millimeter (mm) objective lenses are larger than 35mm lenses.

Larger objective lenses allow more light to reach your eye than smaller lenses. This is important especially when trying to view an object in dim light. The tradeoff is that the larger objective add more weight to the binoculars.

As you review the list of a pair of binoculars' features, also take note of the field of view. Field of view refers to how large an area can be seen through the optic lenses at a certain distance. Binoculars with a 60-degree or larger field of view are considered to be wide angle. As such, wide-angle binoculars are often preferred by sportsmen and wildlife watchers since it is usually easier to locate deer, birds and other animals at a distance.

Also, it is important to see if the lenses are coated. As strange as it may sound, the thin coating applied to lenses plays a significant role in determining an image's brightness and how true are the colors as viewed through the binoculars.

Optical experts have found that 5 percent of the light reaching the objectives in a pair of uncoated lenses is lost before it ever reaches your eye. Compare this to the 1 percent of light lost through a finely craft pair of coated lenses. While the difference may not sound like much, it is huge when you are viewing wildlife in low light conditions as I was on my first ornithology field trip.

Various coatings are applied to help provide the user with images that best represent the true color of the subjects viewed. This is extremely important to those of want to enjoy the natural colors of flowers, butterflies and birds.

As you might expect, there are a number of different types of coatings, such as coated, fully-coated, multi-coated, fully multi-coated and phase coating. I will not go into the nuances of the various types of coating. However, I will say that some of the very best binoculars you can use for looking at birds come with a phase coating on one face of the prisms mounted inside the binoculars.

When I began using binoculars, only the most expensive models were waterproof. As such, having fog and water droplets form inside one's binoculars were perennial problems. That is not the case anymore. Even many of the least expensive binoculars are waterproof. But, if you want to buy a pair that has the best protection against water, look for a model that is either water and fog proof or nitrogen filled and sealed.

Armor coating also was once a high-priced option. Not anymore. Armor-coated binoculars are now within most folks’ price range. The coating can really help reduce damage incurred by dropping a pair of these delicate optics.

Another feature you should consider is eye relief. If you wear glasses and don’t want to take them off when you look through a pair of binoculars, choose binoculars that have long eye relief. If you wear glasses to clearly view objects at a distance, buy a pair that has an eye relief of 16 to 18 or more.
It is also important to know a binoculars' focusing distance. Most binoculars have a focusing distance of 12-20 feet. That simply means that you will be unable to focus on anything closer. With that in mind, if you plan on using your binoculars while hunting, watching birds through your back window and looking at butterflies, buy a pair of close-focusing binoculars. Some of these binoculars can focus at things only 3-6 feet away. For this reason, close-focusing binoculars are used extensively by people who enjoy watching butterflies.

I have found that it is always best to try out different models of binoculars before buying a pair. Also, ask your friends if you can try their binoculars, and learn what they like or don’t about their pair. Talk to a salesman or –woman who knows the various features available in a pair of binoculars. Some of the best help I have ever received has been from representatives of online businesses that deal in a number of different brands of binoculars. You can even compare the customer ratings of models. All of this information will help you find a pair that is the right weight, size and magnification for your use.

Note: Often one of our eyes is stronger than the other. To prevent dizziness and eye strain, each pair of binoculars has to be adjusted to fit the user. Begin by adjusting the distance between the eyepieces. Move the barrels of the binoculars to a point where the eyepieces are directly in front of your eyes. Then, just below one of the eyepieces (usually the right one) you will find a series of markings. Close the eye that looks through that lens (say, the right eye), and using the focus knob, bring a distant object into sharp focus through the other barrel. Next, open your right eye and rotate that eye piece adjustment (diopter) until the object is also in focus through the right lens. On the binoculars you buy, once you determine the proper diopter setting, make a mental note of it. If the adjustment is moved later, you can quickly return it to the proper setting.

Finally, I urge you to buy the best binoculars you can afford. A pair of binoculars is a long-term investment. Buying the right ones helps ensure that, for years to come, you will be able to see the natural world in a way that is impossible with the naked eye alone.

Terry W. Johnson is a former Nongame program manager with the Wildlife Resources Division, a backyard wildlife expert, and executive director of TERN, the friends group of the Nongame Conservation Section. (Permission is required to reprint this column. Contact rick.lavender@dnr.ga.gov.) Learn more about TERN, The Environmental Resources Network, at http://tern.homestead.com. “Out My Backdoor” archive.