National geographic porro prism zoom binoculars 50mm national geographic 9019000 these 7 x 50mm binoculars from national geographic are elegant porro prism binoculars with excellent optical characteristics through the green fully coated optics the light transmittance and colour reproductioncontrast is significantly improved a diopter adjustment is naturally present ideal for first experience in bird and nature watching the 7x magnification provides a steady image even on windy days th