Marine binoculars underwater binoculars area of use watersports magnification 7 x lens diameter 50 mm prism system porro exit pupil diameter 71 mm min focus distance 106 m angle of view 697 field of view in 1000 m 122 m focussing system individual focus viewing straight binocular weight 1 050 g special features for spectacle wearers rubber armouring outdoor function waterproof