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Message: <blockquote data-quote="Troubador" data-source="post: 3148718" data-attributes="member: 109211">In response to Bruce's suggestion (see below) I will demonstrate my optical ignorance (again) by asking a naive question.Quote: Originally Posted by Troubador View Post Bruce I would lay money (especially somebodyelse's ) that the big field of view contributed a large portion of the impression of brightness too simply because there is so much sky in the view.Lee A good point. That is something I have wondered about in the past when doing comparisons for brightness. That might make for a good topic of discussion in a new thread. /INDENT] When I started out buying bins the adverts stated that 42s were brighter than 32s and the impression given was that the 42 mm objective lenses grabbed more light. At the time therefore I imagined that the view through a 42 had more light per square mm than that from a 32. I don't recall anything about brightness being exit pupil - dependant. In fact I don't recall anything about exit pupils at all, but maybe I skipped over this concept not understanding what it was. OK so I understand today that brightness is largely dependant on exit pupil size apart from the issue of high transmission glasses which do allow more photons per square mm to pass, even if perception of the benefit is controversial and may vary from person to person. But what about wide-angle eyepieces? Don't they capture a larger area of the image created by the objective lenses and squeeze it into the exit pupil? And if so doesn't this necessarily mean that more photons per square mm are squeezed into the exit pupil. In short, doesn't this mean that wide-angle bins are brighter?? OK, I've stuck my head up above the parapet, so start shooting :smoke: Lee</blockquote>

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