Objective lens (also known as the “aperture” of the binoculars): A set of technical detail imprinted on any pair of binoculars could be something like this: 8×42, or 10×50 or 10×25. The second number (42, 50, 25) is the diameter of the objective lens (in millimeters), i.e. the two big lenses at the front of the two barrels. The bigger the objective lens, the more light is captured, resulting in a clearer and brighter image, which is important when used in fading light or when focusing on something in the shade of a tree. However, bigger lenses also means more weight, so this has to be kept in mind when considering to buy a pair.