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• Magnification or Power
  Binoculars are referred to by two numbers such as 7x35. These numbers is imprinted on the binocular body. The first number is the magnification or power of the binocular. With a 7x35 binocular, a 7x power means that you are magnifying something 7 times  larger than you would see it with the unaided eye. Please remember that as magnification increases, brightness and field of view tend to decrease.
• Objective Lens Size
  Binoculars are referred to by two numbers such as 7x35. These numbers is imprinted on the binocular body. The second number refers to the diameter of the objective or front lens. The larger the objective lens size, the more light it gathers, and the brighter the image.
• Exit Pupil
  Refers to the size of the circle of light visible at the eyepiece of a binocular. The larger the exit pupil, the brighter the image, and the better they are for low light situations. The exit pupil is calculated by dividing the diameter of the objective lens by the magnification power (a 7x35 model has an exit pupil of 5mm). An exit pupil size of 2 or 3 mm is enough for viewing objects in  daylight, an exit pupil size 5 or 6 mm is for dawn to dusk lighting, and 7 mm for nighttime viewing.
• Field of View (F.O.V.)
  Refers to the width of the viewing area seen through the binoculars. This number is imprinted on the binocular body. It is defined by the width in feet or meters of the area visible at 1000 yards or meters. Wider field of view make it easier to find and track a moving subject. Generally, F.O.V. decreases as magnification increases. 
• Eye Relief
  Refers to the maximum distance a binocular can be held away from the eye and still present the full field of view. For eyeglass wearers,  extended or long eye relief can reduce eyestrain. Generally, a binocular with 13 mm or more of eye relief is considered long eye relief.
• Near or Close Focus
  Refers to the shortest distance at which the binocular can provide a sharply focused image of an object.
• Prism Glass
  Most optical prisms are made from borosilicate (BK-7) glass or barium crown (BAK-4) glass. BAK-4 is higher quality glass yielding brighter images and high edge sharpness. Generally, higher quality binoculars use BAK-4 prisms.

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• Compact Binoculars
  Compact Binoculars generally utilize the roof prism design,  the objective lenses and the eyepiece centers are lined up creating a compact design with full size power.  Some of compact binoculars will fit into jeans pockets, so they are the good choice to take along to the theater or on hikes and hunting trips.
• Full-Size Binoculars
  Full-size binoculars generally utilize the porro prism design, the objective lenses and the eyepiece are offset.  A standard or full-size binocular can be used for everything such as nature observation, hunting, boating, and sports.
• Wide Angle Binoculars
  Wide angle binoculars are designed to have large field view without sacrificing magnification or power. It is ideal for tracking fast-moving action across wide areas such as football fields, racetracks and wilderness terrain.
• Zoom Binoculars
  Zoom binoculars have two power numbers which means your can change magnification or powers. It allows the user to increase the magnification in order to focus in on the details or reduce the magnification in order to get large field of view. It’s like having several binoculars in one! 
• Waterproof Binoculars
  Each type of binoculars listed above can be waterproof or fogproof. Waterproof binoculars are O-ring sealed and nitrogen purged for reliable waterproof and fogproof performance. Waterproof binoculars can deliver clarity in bad weather conditions including fog and rain. 

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There are two basic types of prism systems on binoculars-porro prism or roof prism. Both types of prism systems offer outstanding optical performance. 

• Roof Prism System
  The prisms overlap closely, making the objective lenses to line up directly with the eyepiece. Binocular with this system are generally lighter, more compact, but also generally more expensive.
• Porro Prism System 
  The objective lens is offset from the eyepiece on each side of binoculars. This system generally provides a wider field of view. 

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• Central Focusing System
  Binoculars are focused by a single focus wheel between the barrels. Both eyepieces can be focused simultaneously. A separate diopter adjustment on right eyepiece allows compensation for the differences between the eyes. Center focusing binoculars are convenient to use, so they are most common today.
• Individual Focusing System
  Binoculars can be focused individually for each eye at the eyepiece. It allows for extra-precise focusing adjustments. It is more often used by mariners and sportsmen.

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Coatings are applied to lenses and prisms to reduce glare and reflection, and to reduce light loss.

• Coated
  A single layer on at least one lens surface.
• Fully Coated
  A single layer on all air-to-glass surfaces.
• Multi-Coated
  Multiple layers on at least one lens surface.
• Fully Multi-Coated
  Multiple layers on all air-to-glass surfaces.

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