The S series of Petnax binoculars consists of a wide array of models. You can find among them porro prismatic, waterproof SP WP devices, SP instruments devoid of any waterproof qualities, and also three roof prism models marked as SD WP.
solid; waterproof casing; moderate astigmatism; excellent distortion correction; lack of coma-related problems; very low brightness loss on the edge of the field; dark areas near exit pupils; sharp images already from 1.7 metres; good quality prisms made of BaK-4 glass; proper blackening and...
too low transmission in the centre of the visible spectrum; bluish cast of images; a bit too high level of chromatic aberration