I was thinking about getting a 10x50 binocular like a Meopta Meostar for low light use which has about 88% transmission, and then I got to thinking is it really going to have more apparent brightness than my Swarovski Habicht 10x40 GA which has 95% transmission but also has a 10 mm smaller aperture. It made me wonder how transmission and aperture interact. How much of an increase in transmission would it take to equal a 10 mm increase in aperture? Transmission makes the cone of light entering your eye brighter and of course exit pupil makes it bigger. As you age we all know your eye can not dilate as much, so you are only able to accept or utilize a smaller exit pupil, and you need 3x more light at 60 as you do at 20 years of age, so I am wondering if transmission doesn't become more important than exit pupil as we age. What do you think?