Porro Binoculars 20x80：
1. Ideal for bird hiking, watching, travelling, shooting and star gazing.
2. Large Bak-4 Roof Prisms and FMC 80mm large lens — ensures the key elements of an optical device, and make the image brighter and clearer.
3. Durable material of aluminum and rubber armor plus ergonomics protection to ensure comfortable and safe use in the outdoor.
The specification of Porro Binoculars 20x80 as follows：
Obj. Lens Dia.
Type of Prism
BAK-4, Porro prism
Exit Pupil Diameter.
Exit Pupil Dist.
Min. Focal Length
Filed of View
The Product Size
Porro prism, also known as Pro prism, is a refractive prism used optically in optical instruments to modify the orientation of images.
it‘s a refractive prism used in optical instruments to modify the orientation of images. It was named after the inventor, Italian Optical Engineer Inacio Pro. The Paul prism is an isosceles right angle three prism made of glass blocks and ends at a right angle. In use, the light enters from the largest rectangular plane in the prism, passes through two total reflections of the inclined plane, and then penetrates the original incident plane. Because the light is in and out of the normal state, the three prism does not play the role of dispersion. But the image that passes through Paul's prism will be turned 180 degrees and will move in the direction it entered, that is, the direction of Paul's prism will also change 180 degrees. But because the image is reflected two times, the partial chirality is unchanged.