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How Many Sets of Lenses Do Binoculars Have?

Binoculars enable you to view a distant object up close. They have been used over the years in many different fields from military use to bird watching. Different sets of binoculars are designed for different purposes; however, all work on the basic same setup. Binoculars use two different sets of lenses to provide the magnified image.

Objective Lens
- The objective lens is the larger set of lenses based at the front of the set of binoculars. According to the Wild Birds Store, the larger the size of objective lens the brighter the image you see will be as more light is allowed in. But in the same sense the larger the objective lens, the heavier the binoculars will be.
Ocular Lens
- The smaller eyepiece lens are referred to as the ocular lenses. These are positioned at the rear of the set of binoculars and are the part of the device you look through to view the magnified image.
Construction
- The two sets of lenses in the binoculars are arranged in either a porro or a roof prism design. In a porro design the ocular and objective lenses are offset from each other, while in a roof prism design they are in line. The shape of a porro design set of binoculars is in the shape of an "M" and a roof prism design is in the shape of an "H." Roof prism designs are smaller and more compact and have closer focusing ability (as short as 4 feet) over porro designs (about 10 feet).
Magnification
- Binoculars are sold with a number designating their magnification such as "8 x 42." This number indicates the power of the magnification will be 8 times closer. The second number is the size of the objective lens in millimeters, in this case "42 mm." As magnification increases, brightness and clarity may diminish depending on the size of the objective lens.

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