Binoculars Explained

Many people use binoculars for watching birds and insects or any object that is far away. A pair of binoculars is often used for watching stars and planets and for identifying constellations in the sky. So what is a binocular? In simple terms, a binocular is an optical instrument that is used for observing distant objects. They work on the same principle as a telescope, but they are more portable and easy to use. The magnification of a pair of binoculars is generally fixed and they are sometimes called field glasses. Many people own a pair of binoculars, but few people know its working principle.

Working Principle of Binoculars

There are many different binoculars available but the most popular ones used by amateurs is the Galilean binoculars and prism binoculars. A binocular is a lot like a telescope and in fact, its construction is like two identical telescopes which are placed next to each other. Since these lenses are mounted side by side, it allows the viewer to look through it with both eyes.

So how do binoculars work? A binocular consists of two objective lenses which are situated at each end of a pair of binocular. The objective lens collects the light from the object that the user is looking at and brings this collected light into focus in the eyepiece lens, which then creates a visible image that is of course magnified to a specified degree. But this image, though magnified, has a serious flaw. It is upside down or inverted in nature. For a telescope, having an inverted image poses no problem, because it does not matter if the stars or the moon is inverted. But for watching a bird or a game through a binocular, you cannot have an inverted image!

So, in a binocular, corrective elements which are also known as prisms are used so that the image is right side up. These prisms are to fix this problem and they are situated between the objective lens and the eyepiece lens. The prisms used in binoculars are nothing but cubes of glass that act like mirrors, without the silver coating on its back. The prisms brings the ray of light from the objective lens closer together with the help of internal reflection. It also turns the image right side up along with the proper and correct orientation. This is the working principle of binoculars.

Binoculars Magnification

When you go to a store to buy a pair of binoculars, you must have noticed some numbers etched or painted on it. This binoculars number is nothing but the magnification power of that particular binocular. Binocular magnification power or binocular power is the number by which the image which you can see through the pair of binoculars has been magnified. If the binoculars power is 6, then the image is six times more magnified then the original image which can be seen by a naked eye. The second number that is etched on a pair of binoculars is the diameter of the objective lens. The size of the objective lens will have a bearing on the overall size of the binoculars. As mentioned before, most binoculars have a fixed magnification. But zoom binoculars with adjustable magnification is also available nowadays. These binoculars zoom however, are not without disadvantages. These include a narrow field of vision, low brightness and contrast, and a bulky frame. While choosing binoculars, it is important to consider its magnification number.

Hope that you will remember the working principle and the physics involved while deciding how to buy binoculars the next time. Binoculars for birding should be simple and light to carry, so that you can watch birds with ease.