Marine binoculars area of use watersports bird watching magnification 7 x lens diameter 50 mm prism system porro exit pupil diameter 714 mm angle of view 75 field of view in 1000 m 1 m twilight factor 187 relative brightness 50 98 focussing system fixed focus viewing straight binocular weight 1 147 g special features rubber armouring outdoor function waterproof