3-9X40 & 4-16X42 UCC Models.
It is the exit pupil and the light transmission quality of the glass and coatings that determines low light visibility and what you can see at sunrise, sunset, and at night. The exit pupil should be as large as the human eye under the same conditions. The exit pupil is calculated by dividing the objective diameter by the power setting on the scope. At night a 40 or 42mm objective scope set on 6 power will give you a 7mm exit pupil which is optimal and matches your eye and transmits the maximum light the eye can see. I keep my Nikon set on 6x for night hunting.
From Leupold: "The key to a scope providing a bright image to the shooter is not how much light it "gathers" but how much usable light it transmits. "Gathers, transmits, what's the difference?" Quite a lot, actually. First of all, rifle scope do not "gather" light, they transmit it. Yes, large objective scopes allow more light to enter the scope, but that by itself does not guarantee that the image will be any brighter than a smaller objective scope's. In other words, the better the glass and coatings you get, the better your night hunting."