There are many factors to consider in choosing the right binocular for an individual’s need. For some it might be choosing the lowest price, color, or style of the binocular. The most important factor in this decision relates to how are you intend to use the binoculars. To most people, binoculars are a simple optical device but in reality they are a complex, precision optical instrument.

What purpose do binoculars serve?
There are two basic functions that binoculars serve. One is that they gather more light than the human eye could on its own. The other is that they enlarge the image being viewed. In order to choose the model that best suits your needs, there are several factors to consider first.

What is the best magnification for me?
The magnification of a binocular is how many times closer an object appears than when viewed by the naked eye. An 8x21mm binocular magnifies the image to eight times its normal size. Typical magnifications range from powers of 7x to 10x, however they are available in much higher magnifications as well. Keep in mind however, that as you increase binocular power, less light will be gathered, and the viewing field will be reduced as well. It is also very difficult to keep an image steady at very high magnifications using a hand-held binocular. A tripod is usually necessary to steady an image at higher magnifications. A good alternative for those seeking the option of high power magnification is a zoom binocular. This gives you the option of higher magnifications without the limitations of a fixed, high power binocular.

What does diameter mean?
The amount of light passing through the different lenses of the binocular depends on the diameter of those lenses. The objective lenses are located at the front of the binocular. The diameter of the objective lenses are measured in millimeters. An 8x21mm binocular has an objective lens diameter of 21 millimeters. The larger the diameter of the lens, the more light they will gather. More light means a brighter image of greater detail and clarity. The size of the exit pupil also affects the brightness of an image. The exit pupil is the diameter of the beam of light, in millimeters, that passes through the eyepieces (oculars) of the binocular. The larger the exit pupil, the brighter the image becomes. Keep in mind however that larger lenses mean larger binoculars, which can become bulky and cumbersome. Most people are willing to sacrifice the slight differences in brightness in return for a compact, more manageable model.

What is field-of-view?
The field of view is the size of the area that can be viewed through the binoculars. Field of view is measured in two ways, angular field of view and linear field of view. The angular field of view is measured in degrees. Linear field of view is the width of area, in feet, visible at one thousand yards. Remember that the higher the power of your binocular, the smaller the field of view will be. In most cases, the larger the field of view, the poorer the image clarity becomes, especially around the edges. Bear this in mind when making your choice. Bigger does not always mean better!

Does the type of prism used make a difference?
There are prisms located inside binoculars that function to flip an inverted image upright. There are two common styles of prisms used; the BK-7 and the BAK-4. The BAK-4 prism is made of a higher density glass and can produce sharper images than a BK-7 prism can. If you are unsure as to which prism is being used, hold the binoculars out in front of you and look through the eyepiece. If you see a square shaped beam of light, chances are a BK-7 prism is being used. A round beam of light indicates the use of a BAK-4 prism.

What are the purpose of lens coatings?
All the optical components of binoculars (the objective lenses, oculars, and prisms) should be coated to minimize light loss and reflection problems inside the binocular. A poorly coated binocular can lose up to 50% of the light initially gathered through the objective lens, resulting in a poor quality image. By coating the optical components with a fine film of certain chemicals, light loss can be greatly decreased. The highest quality binoculars have multiple coatings on all the optical components. These are known as "fully multi-coated" binoculars. These binoculars have the least loss of light and the result is a higher quality image.

What is eye relief?
Eye relief is the distance, in millimeters, a binocular can be held away from the eye and still see the entire field of view. If you wear glasses, a longer eye relief would be advantageous since your eyes cannot get as close to the eyepiece.

How can I get the most out of my binoculars?
Once you have chosen a binocular that is right for you, there are several things you can do to ensure that you are getting the most out of your binoculars. Thoroughly check your binoculars when you first buy them. Make sure there are no scratches, dents, or any other obvious damage to the unit. Check for image clarity, brightness and ability to focus. If you see blurred or double images, your binoculars may be damaged or poorly made.

What steps can I take to maintain my binoculars?
Make sure your lenses are clean at all times. Keep them free of fingerprints, dirt and debris. Use a Carson LensPen to clean your lenses quickly and safely. When not in use, always replace the lens caps and store your binoculars in a case.

How do I focus my binoculars properly?
There are several steps you should take to focus your binoculars. The first step is to close your right eye and look through the left side of the binocular. Turn the center focusing wheel until you have a sharp image. Then close your left eye and look through the right side. Turn the dieter eyepiece until you have a sharp image in that eye. Last, look through both eyepieces and use only the center focusing wheel when looking at objects at different distances. Now you are ready to fully enjoy your binoculars.

* Information supplied by Carson Optical

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