Objective - Binoculars
In the world of binoculars, the term, objective, is often erroneously used to refer to the front lens. In fact, the front lens is the foremost lens of the objective itself.
An objective is actually a lens system. So, when someone refers to a lens, they often mean an objective. Can you still follow this?
The diameter of the foremost or front lens of the objective determines how much light enters the binoculars and therefore greatly affects theclarity and brightness, the exit pupil and the twilight factor of the binoculars.