Binoculars are not as simple as many people think. They are a much more complicated than the idea that most people have that they are just a pair of magnifying glasses in fancy casing. They are highly technical and employ some very basic techniques of optical physics and are of various types with very technical differences.

Before buying a binocular, you must find out what kind of prism you need in your binocular. The prism is responsible for enlarging the image and setting it right side up, and without it you would be looking at an upside down image, which would be highly frustrating. The prism lengthens the light path between the objective lens and the eyepiece and that is how you get a magnified image using a binocular. There are various types of prisms and lengthening the prism inside the binocular can give you a sharper and more magnified image without increasing the size of the binoculars.

There are two main types of binoculars classified on the basis of prisms used:

• Porro prism binoculars
• Roof prism binoculars

Porro prism binoculars have objective lenses that are offset from the eyepieces. They are bigger than roof prisms which have two straight tubes and whose objective lenses are straight in line with the eyepiece. This makes them small and compact. But Porro prism binoculars allow for a much sharper image and have less light loss as compared to the roof prism binoculars.

Even though the Porro prism binoculars look more expensive, the roof prism binoculars cost more to make since the internal setup of the prisms is more complicated than that of the Porro prism binoculars. The roof prism binoculars have a more complex light path and require absolute precision during manufacturing. But since they are compact and easy to carry, they are very popular with observers, especially those who like to travel light but with all their gear.

The Porro prism binoculars were very famous in the 1960s, but they aren’t obsolete today even in the presence of the roof prism binoculars. The reason is simple – even the less expensive Porro prism binoculars allow for better performance, sharper images, and less light loss because of the simple internal prism setup. This makes them an observer favourite still.

Another comparison point between the roof prism and porro prism binoculars is that most of the latter type models are not waterproof and rugged, which makes them prone to breakage and damage. The roof prism binoculars, on the other hand, are made to be durable and long-lasting. So, before you head out and buy binoculars, decide on the kind of prism technology you want and how much you are willing to spend as roof prism binoculars are a little more expensive than Porro prism binoculars.