What Are Binoculars?
Binoculars: are a pair of identical or mirror-symmetrical telescopes placed side by side (one for each eye) and aligned to point accurately in the same direction. Most binoculars are built to be hand held, although sizes vary widely from super compact opera glasses to large tripod mounted mounted military ones.
What Do The Numbers Mean?
|Magnification (power)||Objective lens (diameter)|
The first number "7" is the power of magnification that the binoculars offer. With "7x" magnification, you'd see things 7x closer than your normal vision.
There are also zoom binoculars. They have variable magnification power. 8x is the main magnification power with the optimum performance. The 16x maginification won't provide brighter and better quality image because the objective lens at the front can't change to follow the magnification power increase.
7x magnification is often chosen by most because it is easier to handle. The higher the magnification is, the more sensitive it is. A little tremble from your hand would feel like a big shake. If you prefer something bigger than 7-8x for a long use, it is recommended to use a tripod. If you have a high powered pair of binoculars with small objective lens, they are better for day time use as a simple aid to see farther.
The second number is the diameter of the objective lens in millimeters.
Large objective lenses are great for light transmission. Large numbers = larger binoculars.
Depending on what your binoculars will be used for, you'd want to find the right one (in terms of size, power and brightness).