How to Choose Binocular Power

Summary: The first step in picking out a pair of binoculars is to figure out the power you should get. This article will help you in choosing the binocular power that works best for your needs.

The first step in selecting a pair of binoculars is determining the power you want. Binocular power is represented by two numbers, as in these examples: 6x24, 7x50, 8x42, 10x42, and 12x36. The two numbers are not directly related; the first indicates the magnification and the second expresses the diameter of the objective lens. -- Magnification -- The first number, which is always the smaller of the two, expresses the amount of magnification that the binoculars allow for. This is an indication of how much nearer the viewed image will seem when looked at through the binoculars. Even though bigger sounds beneficial, this is not always the situation with binoculars. Picking the correct magnification will vary depending on your intended usage. Lower magnification binoculars-typically those that are 7x and lower- allow for a larger field of view which makes targeting objects far away-like animals, ships, or birds-easier. A larger field of view also makes it easier to follow movement of the object being observed. Since lower magnification binoculars take in more of the scene, they collect more light. As a result, the resulting image will usually be easier to see and brighter even though it is not as greatly magnified. Because of the reduced magnification, they also tend to be less sensitive to movement or vibration. If you intend to be in the field making use of your binoculars without a tripod, this can be a critical consideration. Lastly, lower magnification binoculars are typically able to focus on objects that are closer by than comparable higher magnification binoculars. But of course, lower magnification binoculars allow for less magnification, and consequently reduced detail when compared to higher magnification models. If you genuinely want high magnification binoculars, typically 11x and above, for your use, make sure you additionally get a tripod or get binoculars with image stabilization. The greater the magnification, the more affected the binoculars are to vibration. Once you starting thinking about 10x magnification binoculars, they will be nearly unusable without an image stabilization system or a tripod. Larger magnification binoculars are also almost always heavy. So if you plan on using them for an extended length of time, a tripod may be a more comfortable choice than binoculars with image stabilization. As for cost, it's probably not surprising that higher magnification models tend to be more expensive than equivalent lower magnification binoculars. Unless you really want or need high magnification binoculars, a good middle-of-the-road magnification amount is 8x. Binoculars at this magnification level result in a reasonable trade-off of magnification while providing low weight, good brightness, and reasonable cost. -- Objective Lens Size -- The second number in the power corresponds to the diameter of the objective lens in millimeters (mm). The objective lens is the lens on the front of the binoculars, furthest from your eye. Smaller objective lens usually indicate binoculars that are smaller in overall size. Binoculars with objective lens sizes of 30 mm and under are usually found on pocket and compact models. While pocket and compact binoculars tend to be lighter and easier to carry, the downside to reduced lens size is that the smaller lenses allow less light into the binoculars. This can result in darker images that are more difficult to see. If you intend to use your binoculars at night, models with smaller objective lenses will not be a good choice. If nighttime use, or brightness is important, objective lenses that are 50 mm or larger will work best for you. However, binoculars with large objective lenses will most often be large and heavy. If you are going to use binoculars that have large objective lenses, you should definitely have a tripod available, independent of the magnification level. The most frequent objective lens sizes used are between 35 and 50 mm. Since the magnification level also affects the brightness of the image (higher magnification is darker), the objective lens sizes tend to go up as magnification increases to balance out the lost brightness. For a good general rule, shop for binoculars that have an objective lens diameter that is at least 5 times larger than the magnification. For example, 6x30, 8x40, 12x60, etc. While there are some binocular manufacturers with exceedingly good optics that will result in excellent brightness at a ratio under 5, the safest thing is to stay at or above this ratio for good brightness.