Prisms decrease the distance light must travel. Without prisms, you would need very long and very heavy binoculars. Prisms allow you to use powerful binoculars without making them significantly larger.

There are two types of prisms: porro prisms and roof prisms. Most regular binoculars use porro prisms. Nearly all compact binoculars use roof prisms.

Learn even more about Binoculars. Continue on or click any of the links below to go directly to that topic.