Bird Watching: Buying Binoculars

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  Chuck Fitzgerald
What To Know When Buying Binoculars
Sports Articles | August 15, 2004

We want you to Get It Right The First Time. Understanding your application is paramount in determining the best fit – for you. Although there are many other specifications and qualities which determine the usefulness of binoculars, we will discuss in this article the primary characteristics for determining the best fit for your application. But before we show you the list, we should go over some basic terminology.

What do the numbers on binoculars mean? All sporting optics (binoculars, spotting scopes, night vision goggles, etc.) use the same nomenclature to describe important features. As an example, a pair of binoculars may have 10x42mm listed as a technical specification. But what does this mean? The "10" refers to the magnification power of the binoculars – that is – objects viewed will appear to be 10 times closer than when they are viewed by the naked eye. The second number in our example is "42mm." This refers to the diameter, in millimeters, of the objective lenses on the binoculars. The objective lenses are located on the end of the binoculars furthest away from your eye when viewing. As with the aperture of a camera lens, the size of objective lens determines the amount of light that can enter your binoculars. If your binoculars are going to be used during low light (hunting and astronomy are good examples) you had better have large objective lenses.
 

Another important number describing binoculars is called field-of-view. A field-of-view of 390' indicates that the width of the sight picture is 390 feet at a distance of 1000 yards. Field-of-view is determined by magnification and the focal lengths of the objective and eyepiece lenses. More magnification always means less field-of-view. This specification is sometimes expressed in degrees. A field-of-view of 6.5 degrees equates to 341' (6.5 times 52.5 equals 341).

How well your binoculars will serve you in low light conditions is described as Twilight Performance. Although many things, such as overall design and quality of glass impact this specification, magnification and objective lens diameter are the chief components. A quick way to determine the Twilight Performance of binoculars is to multiply the magnification power (first number) times the objective lens diameter (second number). The higher the result, the better the Twilight Performance. As an example, 10x42mm binoculars will have better Twilight Performance than 8x50mm binoculars (420 versus 400).

Now that we understand some basic terminology, here is “What to Know When Buying Binoculars."

* While compact binoculars weigh as little as a pound, by using them you will undoubtedly sacrifice performance. If performance is your main consideration, full sized binoculars are preferred. Anything weighing over about 1.5 pounds will get heavy fairly fast. Use a binocular support system to evenly distribute the weight across your shoulders instead of using a strap around your neck.
* The amount of light available while using your binoculars will determine –more than any other consideration – which binoculars are best for you. Low light uses such as hunting, birding and astronomy require larger objective lenses.
* The distance you will be from the object you view will determine the magnification power required in a pair of binoculars. If your application is bird watching, theater or sporting events, a low powered binocular will suffice in most cases. But if you're into astronomy, you'll need a high powered pair.
* The minimum focal point in binocular terminology refers to how near an object can be to you and be still be viewed in focus. This tends to be important for birding but not so important for most other uses.
* Binoculars with a magnification power greater than 10x (and without a stability feature) will be difficult to hold steady. This becomes important when viewing the night sky or distant mountains. A tripod may be a good thing to have if you’re using binoculars with high magnification.
* Using your binoculars outdoors will usually subject them to moisture. Waterproof binoculars are preferred for all marine, hunting, birding and other nature related activities.
* The greater the magnification, the narrower the field-of-view. If field-of-view is important to you, don't purchase the most powerful binoculars you can find. This becomes very important when viewing objects that move quickly such as antelope, race horses, shooting stars or race cars.
* As with almost everything else in life, with binoculars you get what you pay for. There are binoculars that cost under $10 and others which cost in excess of $2,500. My experience says you will need to spend at least $250 for a pair of binoculars worth having.
* There is no such thing as “one-size-fits-all” when it comes to sporting optics. If you have multiple uses for binoculars, you will most likely end up with multiple pairs of them – and that’s O.K.

Your understanding of these few simple tips will not only help you in acquiring the correct binoculars for your application, but they will also help you with successful viewing – no matter what you’re looking at. Use this information and you’ll Get It Right The First Time. Get Outdoors!

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