Binoculars

Focus in on binocular components, construction, and features with our shopping guide. 

How To Buy Binoculars

Binoculars can be used for a host of outdoor and indoor activities, from bird watching to football games, to concerts. No matter what activity you use them for they will always serve the same purpose: to improve your view of a distant subject. However, how you plan to use your binoculars, and where and when, are critical to the binocular selection process. 

The pair of binoculars you buy will probably end up lasting you a lifetime. Therefore, it is important to take a look at all the different features in order to determine which features are really important to you.

Features to Consider:

Magnification/Lens diameter

• Every pair of binoculars has a reference number that tells you its magnification power. A standard number would be 6 x 30.
• The number 6 refers to how many times the binoculars will magnify an object; in this case, it will appear 6 times closer than it really is
• As a general rule, higher magnification will make it more difficult to pick up moving objects, such as birds
• The 30 number indicates the diameter of the front of the binoculars, or the objective lens
• The objective lens gathers the light that will eventually reach your eyes
• In general, a larger objective lens means more light will be let in the viewing area, also known as the field of view, and it will be larger
• A larger lens diameter; however, does mean a heavier pair of binoculars

Brightness

• Binoculars come with a variety of brightness levels, which is basically the amount of light your binoculars let in
• The primary deciding factor in determining brightness is the size of the exit pupil, which is the size of the beam of light your binoculars allow in
• A larger exit pupil will allow in more light, which is a benefit if you plan to use your binoculars in lower light conditions but not as desirable if they will be used outdoors in the sunshine
• To determine the size of the exit pupil, divide the lens diameter by the magnification power
• A 3-mm to 5-mm exit pupil is generally adequate for normal viewing. A 7-mm is best for low-light use.

Prisms

• The purpose of a prism in binoculars is to correct the inverted and reversed images you would see in their absence
• The prisms are located inside the binoculars and they transmit light from the objective lens to the eyepiece
• Binoculars come in two prism designs: porro prism and roof prism
• A porro prism offsets the eyepieces from the objective lens to allow more brightness to be let in. However, this makes the binoculars larger.
• A roof prism aligns the lenses in a straight configuration, which makes the design smaller. This preferred size is a consideration, but the image is not as bright as with a porro prism.
• Most binoculars have a standard BK-7 prism glass

Field of view

• This is the measure of how much you can see through your binoculars at 1,000 yards
• Generally, the higher the magnification, the less the field of view
• This information is always printed either on the instruction sheet or directly on the binoculars
• The field of view for a 7x binocular is usually 7 degrees, or 369 feet
• A wider field of view, up to 9 degrees, is considered a wide-field model and is best for wildlife viewing

Focus

• There are generally three focus features on each pair of binoculars
• Some binoculars offer fixed focus, which is convenient but loses the ability to alter the focus for personal needs
• A center knob lets you focus both barrels at the same time
• The right diopter ring, located on the right eyepiece, allows you to customize your focus for each eye
• Binoculars are also ranked on near-focus distance, which is simply how far away you must be from your subject before it can be properly focused. The general range is 10-40 feet.

Selecting the right binoculars

• Use the following guide to help choose the proper magnification for your binoculars:
• Indoor sporting events, theater/opera: 6 x 30
• Hiking, light bike touring, nature walking: 7 x 25
• Outdoor sporting events and concerts, boating, wildlife observation, general purpose: 7 x 35
• Star watching, hunting, bird watching, general purpose: 7 x 50
• Long-distance bird watching, star watching: 8 x 40

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