Almost all binoculars falls into one of two types. Those types are roof prism binoculars and porro prism binoculars.
Roof prism binoculars were created as early as the 1870s and much work on it was done by Achille Victor Emile Daubresse. Roof prism binoculars have less internal parts than a porro prism binocular. Roof prism binoculars also are easier to keep clean and easier to keep dry. Roof prism binoculars have a front lens that is in direct line with the rear lens.
The front lens is the objective lens while the rear lens is the ocular lens. Being in direct line allows this binocular to be more compact. The depth of field can present problems when using roof prism binoculars. Most roof prism binoculars use prisms that were designed by Ernst Karl Abbe and Albert Koenig or the Schmidt-Pechan prism. With these prisms the image is first erected then folded along the optical path.
Porro prism binoculars were invented by Ignazio Porro in 1854 and further improved by Carl Zeiss. Unlike the roof prism binoculars the objective lens is not lined up with the ocular lens. Therefore these binoculars require occasional recalculation by a professional. When used the objects usually appear brighter than when using a roof prism binocular. They are usually cheaper to produce and cheaper to buy than the roof prism binocular. They are harder to keep clean and water can damage these binoculars severely.
There are many similarities and differences in these two types of binoculars.
