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Message: <blockquote data-quote="RJM" data-source="post: 1688050" data-attributes="member: 66340">There is a school of thought (I think derived from astronomical observation) that says since your pupil dilation normally does exceed 2-3mm during daylight hours, any binocular that produces larger exit pupils is a "waste" of light.  I am not so sure what is true at night is true during the day based on my own experiments. A larger exit pupil binocular is almost always easier and more enjoyable to look through and that alone may be why they can sometimes seem "brighter". But I suspect just bringing the binocular to your eye causes the pupil to dilate more than the normal 2-3mm since it is now deeply shaded by the eyecups. I have not been able to come up with a suitable test to "prove" my hypotheses though. Now that technological advances allow many 42mm bins to approximate the size/weight of their 32mm brothers, I prefer the larger aperture and a 7x-8x mag for the steadier and wider fields. But I also have a small Nikon ED50 fieldscope and Canon 18x50IS when higher mag is the necessity of the day. happy 2010,Rick</blockquote>