The other day I bumped into a friend at a local department store who was in the process of deciding on which pair of binoculars to buy. She asked me for some advice.
I hesitated.
My first inclination was to say she would be better off dealing with a store that specializes in quality optics and binoculars. However, I responded by saying there are a number of factors that should be considered before making such a purchase.
All binoculars, regardless of where they are made and the manufacturer, are labeled with two numbers such as 7x35 or 8x40 and so on. The first number refers to the magnification – how many times an image is enlarged over normal when you look through the binoculars. Think of magnification as how many times closer the subject appears to be than it is in reality.
A pair of binoculars with an eight-times magnification makes the subject appear to be eight times larger, or eight times closer than it really is. An 8x50, 8x40 or 8x20 pair of binoculars all magnify an identical eight times. (With zoom binoculars the first two numbers represent the zoom range. In a 7-15x35, for instance, you can actually change the magnification from seven to 15 times.) Choose this first number carefully because more is not always better.
This is especially true of magnification. As magnification goes up, image brightness goes down. Field of view (the amount of territory seen through the binocular) also goes down. And, just as importantly, image steadiness goes down. Binoculars magnify not only the image, but also every shake and tremble in your hands.
The second number on a binocular - the 35 in 7x35 or 40 in 8x40 - is the diameter (width) of each front lens, measured in millimeters. This number directly affects performance. When magnification and quality is equal, the larger the second number, the brighter the image as well as the sharper the image. An 8x40 pair of binoculars, will produce a brighter and sharper image than an 8x25, even though both enlarge the image an identical eight times.
The larger front lenses of an 8x40 or 8x50 pair of binoculars produce wider beams of light that exit the eyepiece. It is simply more comfortable to view with an 8x40 pair of binoculars than an 8x25.
By the way, the second number is not the field of view as many people mistakenly believe, nor does it affect the field of view. Field of view is the amount of territory you see when you look through the binoculars. It is determined by magnification and the type or design of eyepiece incorporated into the manufacture of the binoculars. Think of a fence 1,000 yards away. If a binocular has a field of view of 372 feet at 1,000 yards, you will see 372 feet of the fence. It should also be noted the diopter adjustment on a pair of binoculars simply allows one to compensate for differences in strength between the right and left eye.
Lens coatings are chemical coatings on the lenses in the binocular to make images brighter. Whenever light strikes a lens, a certain percentage of light is lost. Since there are a number of lenses used in a binocular, binoculars without coated lenses can lose as much as half of the incoming light.
Once you have determined which type of binoculars best suits your need, then it’s simply a matter of finding the best price. The bottom line though, is that you usually only get what you pay for. There is also the matter of warranty coverage.
After that, it’s pretty much a matter of getting out and enjoying your new purchase.