What is a porro prism?
A17. A porro prism is an image erecting system that was designed and patented by the Italian optician, Ignazio Porro in the 1850’s. Today, porro prism binoculars use a porro prism in a double prism Z-shaped configuration to erect the image, resulting in binoculars that are wide, with objective lenses that are well separated and offset from the eye pieces. In other words, the eye piece and the objective lens in a porro prism are never in a straight line. A porro prism is a larger and bulkier prism than a roof prism; and because of this, the body of a porro prism binocular will also tend to be bulkier. Porro prism binoculars inherently produce brighter images than roof prism binoculars of the same magnification, objective diameter and optical quality; and are less expensive to make than a roof prism. This makes a quality porro prism binocular every bit as good optically as a quality roof prism and at a much lower cost. If your priority is getting the most optics for your dollar, especial
