Binocular
The exact definition of the word binocular that you will find in an English language dictionary (as given in infoplease.com) is "an optical device, providing good depth effect, for use with both eyes, consisting of two small telescopes fitted together side by side, each telescope having two prisms between the eyepiece and objective for erecting the image." That's why they called 'bi'-nocular, because 'bi' means two in Latin.
There are a lot of important characteristics about a binocular that you must be aware of if you are about to buy one, or you just want to get some information on the topic. Some of the terms that will be described here are - magnification, objective size, prism type, focus type, speed of focus, eye relief, lens coatings, armoring and weight. Bottom line is that those parameters determine what is the specific application of a given binocular, and hence determine whether or not, the given model will suit your particular needs.
Magnification is how many times close an object appears compared to viewing it with a naked eye. A magnification of 10 means that the image you being viewed appears 10 times close than it actually is. Have in mind that as the power of magnification increases, the quality of the image goes down. And the other interesting fact is that the power of magnification is in direct relationship with the size of the objective lenses, so the larger the diameter of the lenses, the higher the magnification power will be. So you need large lenses to get a higher magnification power, but that on the other hand makes the whole binocular bigger and heaver. That's why there are two types of binoculars - traditional and compact. The compact ones have lower levels of magnification, but they can fit in your back pocket. On the other side, traditional binoculars take you closer to the action, but are heavier to carry.
The objective size is the diameter of the lenses given in millimeters. The reason why you get better magnifying power with larger lenses is that they get more light, and more light means brighter and clearer image. A 50mm or 56mm lens is considered large and will definitely allow you to see more details, especially if you hunting at night. Perhaps the best balance between performance and portability is a 30 or 32mm objective lens. If you examine the description of a given binocular model, perhaps the first thing you will notice is for example 10x25. The digits before the 'x' signify the magnification power, while the digits after the x are the objective size. The prism types available are porro prisms and roof prisms. The porro prisms are the older design, while the roof prism are the new straight, barrel body design. Logically, roof prisms are more expensive to produce, but provide better durability, longevity and image quality.
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