I like a 4mm exit pupil or larger. The human pupil dialates from about 2mm in bright light to about 7mm in low light/ dark. An exit pupil larger than your pupil isn't exactly wasted, in that your...

The average pupil on a human is 3 to 4 mm. If you have a exit pupil of 4 ( in other words objective size divided by the magnification ) then all your pupil is covered with the light that you are...