Understanding binocular brightness
Our binoculars offer objective lens diameters from 25mm (e.g. the 8x25 IS) to the brightest 50mm (e.g. the 15x50 IS AW). Given the same magnification, 10x42 binoculars are approximately twice as bright as a 10x30 pair, 50mm and 42 mm binoculars with a larger exit pupil diameter (the objective lens diameter divided by the magnification) deliver a brighter, wider and clearer view and are bigger and heavier.