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Message: <blockquote data-quote="Tom Bombadil" data-source="post: 3182041" data-attributes="member: 33331">If one is out in bright sunlight and their pupil size is down to 2.0 mm, then wouldn't you be using only 16mm of the objective, through an 8X bino?    That is, in an 8x32 the exit pupil is 4.0mm, and through the 8x42 it is 5.25mm.   But if your own eye pupils are only open 2mm, then most of the light gathered by the objective will go unused.   Same for if you had an 8x56.Wouldn't the perceived image brightness be the same through 32 or the 42 if they had the same transmission?  If your pupils were open to 6mm, then it would make a big difference.</blockquote>