re: Rifle scope recommendations

There is a beam of light exiting the lens. The size of the beam is a function of the zoom and objective lens. If there is a smaller beam of light than the size of your pupil, you won't be getting the maximum volume of light in your eye possible. If the beam of light is larger than your pupil, you're getting the maximum amount of light possible from the scope.

Like it was said earlier, it doesn't have anything to do with brightness. Exit pupil is more like volume while light transmitted is more of a quality thing.