The history of binoculars started almost two centuries ago in 1825, when J. P. Lemiere discoveredthe advantage of placing together two telescopes in the same frame.

At that time, the telescope had already been in use for around two hundred years, coming to life as a result of human curiosity and inventiveness.

The literal meaning of binoculars is two eyes- coming from the Latin.

Read this simple explanation about how binoculars work...

Binoculars how do they work

Unlike the telescope, with binoculars:

• you don't use both eyes to view the object

• you don't need to close one eye when viewing

• you get a three-dimensional image

Binoculars how do they work - three parts

Binoculars consist of three important parts:

• they eyepiece lens, which is the smaller lens, and which you hold close to your eyes• the objective lens, which is the larger lens, and which is furthest from your eyes

• a prism inside the binoculars, and which acts as a mirror

Binoculars have the ability to refract light...First of all, the objective lens captures the light from whatever you're viewing, magnifies it, brings it to focus in the eyepiece, where it's transformed into a visible image.

However, if binoculars just consisted of these two lenses, the image you see would be upside-down.

To rectify this, and turn the image the right-way-up, a prismis buried inside the binoculars.

What is a prism?

A prism is a solid piece of glass, which acts as a mirror, but without a mirror’s reflective backing, and its job is to make the image appear the right-way-up.

Why do you need to keep the smaller lens next to your eyes?For the simple reason that, if you looked through the binoculars the other way, the image would appear even smaller and further away than it really is.

Binoculars how do they work - prisms

As already explained, the prism takes the upside-down image and turns it up once more so that it faces the right way.

This image is then transmitted to the smaller lens, where you'll see the object magnified and correct.

There are two main types of prism:

• porro prism

• roof prism

Binoculars how do they work - porro prism

The porro prism tends to be the most popular.Patented by the Italian, Ignazio Porroin 1854, this image-erecting system was later refined by manufacturers such as Carl Zeiss.

You can tell a porro prism binocular, because the objective lens is well-separated from the eyepiece.

These binoculars usually give an excellent sensation of depth, and produce a brighter image than roof prism binoculars - all other factors being equal.

However, they tend to be heavier and more bulky than roof prism binoculars, and occasionally need re-alignment.

Binoculars how do they work - roof prism

You can tell roof prism binoculars because the objective lens is approximately in line with the eyepiece.

Although narrower and more compact than porro prisms, they do tend to be more expensive to produce, and don't give such a bright image.

However, they don't usually need re-collimation.

Binoculars how do they work - early binoculars

The earliest binoculars tended to be used by the upper classes, mainly to view the stage in theaters, and they employed what is known as Galileanoptics.

In other words, instead of using two convex lenses, they used a convex objective lens and a concave eyepiece lens.Galilean optics are still used today for opera or theater binoculars, and some other cheaper models.

However, their field of view tends to be narrow, and they're unable to produce very high magnification.

What You Should Look For In Binoculars

Choosing Your Binoculars Magnification

Different Types Of Coatings

Which Are The Best Binoculars

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