Roof prism, Porro prism, and reverse Porro prism binoculars each use image-erecting prisms to provide correctly oriented images. Without prisms, the image would always appear upside down and reversed. Most of us recognize the Porro prism as a "classic" binocular design with offset prisms while the roof prism binocular is shaped like an H: more streamlined and compact. The size, type, and quality of the prisms used in a binocular's design affect the clarity of the image. You may prefer one style over another based on its ergonomics. Since roof prism binoculars are more expensive to manufacture, economics will also be a factor in choosing which style is best for you.
Porro Prism Binoculars
Porro prism models will deliver good optics for the dollar, but lack the durability and compact styling of roof prism models. In addition, many Porros are not waterproof.
Reverse Porro Prism Binoculars
This design allows for a compact binocular that easily fits in your hand.
Roof Prism Binoculars
In recent years, the popularity of the roof prism design has increased dramatically. These binoculars are rugged and durable, and you no longer have to spend more money to get good optical quality in this design.