How to Choose Binocular Power

The first step in selecting a pair of binoculars is determining the power you want. In these examples, binocular power is represented by two numbers: 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 the binoculars allow. This indicates how much nearer the viewed image will seem when viewed through binoculars. Even though more prominent sounds beneficial, this is not always the situation with binoculars. Picking the correct magnification will vary depending on your intended usage.

Lower magnification binocularsâ€” typically those that are 7x and lowerâ€,” allows for a larger field of view which makes targeting objects far awayâ€” like animals, ships, or birdsâ€” easier. A larger field of view also makes it easier to follow the observed object's movement. 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 magnified. Because of the reduced magnification, they tend to be less sensitive to movement or vibration. Using your binoculars without a tripod can be a critical consideration if you intend to be in the field. Lastly, lower magnification binoculars are typically able to focus on objects closer than comparable higher magnification binoculars.

But of course, lower magnification binoculars allow for less magnification and consequently reduced detail compared to higher magnification models. If you genuinely want high magnification binoculars, typically 11x and above, for your use, make sure you get a tripod or binoculars with image stabilization. The greater the magnification, the more affected the binoculars are to vibration. Once you start thinking about 10x magnification binoculars, they will be nearly unusable without an image stabilization system or a tripod. More giant magnification binoculars are also almost always heavy. So if you plan on using them for an extended time, a tripod may be more comfortable 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 want or need high magnification binoculars, a perfect 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 affordable cost.

-- Objective Lens Size --

The second number in 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. A smaller objective lens usually indicates binoculars that are smaller in overall size.

Binoculars with objective lens sizes of 30 mm and under are usually found on the 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 essential, objective lenses that are 50 mm or larger will work best for you. However, binoculars with large objective lenses will often be large and heavy. If you use binoculars with large objective lenses, you should have a tripod, 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 image's brightness (higher magnification is darker), the objective lens sizes tend to increase as magnification increases to balance out the lost brightness. For a good general rule, shop for binoculars with an objective lens diameter at least five times larger than the magnification. For example, 6x30, 8x40, 12x60, etc. While some binocular manufacturers have 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.