I'll probably mess this up bad however the maximum size image that the eye pupil can process is 5MM..to determine the binoculars image output divide the objective size(big end) by the small end size...the result is the image output size. In theory anything OVER 5MM cannot be utilized and anything LESS than 5 MM is not taking full advantage of the eye's maximum pupil size.

I'm old and back in that day preferred sporting binoculars were usually

7X35
8X40

There are things that may be as or more important than image/pupil size however I've tried to stick with that and has served me well. I did try and gave up on an excellent 12X50 but only because the power was too high for me for extended hand-held viewing [primarily colony varmints]. 7-8X works for me and I would probably not buy 10X or above based on my experience.