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Binoculars enhance the size of the object you are watching and makes images look brighter even in low light conditions by letting more lights in the device. There are two optical systems in binoculars having a common focus system, enabled through the hinge they remained connected by. Therefore, this device projects an image for both eyes simultaneously. There are different kinds of these devices available in the market and they are Standard Full Size, Zoom, Binocam, Foldable Compact, Waterproof, Wide Angle, and Focus Free. These are the basic categories in which binoculars can be classified. Without getting into further details of types, let's move to the factors that determine performance of the device. The three main factors are lens diameter, magnification, and optical coating. Now, let us check these features one after the other.
Magnification - This is the extent to which the object you are viewing gets enlarged. Binoculars are generally marked by a combination of numbers separated by 'x'. In 7x50, 7x is the extent of magnification. A binocular with 7x magnification means it can enlarge an image seven times than the normal size. Higher magnification reduces field of view, on one hand, and makes images brighter, on the other. In accordance with usage, power of binoculars vary. 6x to 8x magnification is preferred for observations during daylight condition. Power from seven to ten is preferred for observations during dusk to dawn. In case, you are planning to use your binocular for observations in mountains 10x to 12x magnifications are considered best. If you are buying this optical device for hunting, you should choose one having a magnification range from 8x to 12x. For water sports, 7x magnification is enough. If the purpose of buying binoculars is solely for astronomy, anything from 15x to 70x should be preferred.
Coating - Coatings are very important in binoculars because significant light gathering capability can be lost, to the extent of 30 per cent, if devices remain uncoated. Once its done, the images will appear brighter. Generally, sharpness of images are highest around the center. However, higher quality binoculars have less difference in sharpness in the center region of images and outer side. There are basically four kinds of coatings popular in the industry and they are coat, full coat, multi coat, and fully multi coat. Two to six magnesium fluoride coatings are applied on eyepieces and prisms for Fully Coated devices, on one hand, and several color layers are coated on objective. Air to glass surfaces are coated with single layer. Four to eight magnesium fluoride coatings are applied on eyepieces and prisms on multi-coated binoculars. Multiple coats are applied on prisms or lenses. Air to glass surfaces come with multiple colored layers. Four to sixteen magnesium fluoride coatings are applied on eyepieces and prisms. Night vision industry especially uses green colored optics. The devices having Blue Coats filter out unnecessary light reflections.
Lens Diameter - Larger objective lenses make images brighter. 20-32 mm is normal for 6x to 8x magnification. 35-50mm diameter is normal for 7x to 9x. 50-70mm is normal for 10x to 36x magnification.
There are three kinds of binocular usages. One for general purpose, another for outdoor purpose, and the third is for the compacts. So, before buying binoculars, you should check the usage type, on one hand, and the factors mentioned above. Only after checking these aspects, you should buy your favorite device.
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