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Message: <blockquote data-quote="ronh" data-source="post: 1806860" data-attributes="member: 55514">Omid,Yeah, non-thing reasons for liking things, huh? But watch out, I will get silly. Regarding your thoughts on the interaction between eye and exit pupil. My 7x50 is extremely easy to use in daylight. But at night, my pupils open to around 6.5mm. Then, the view is extremely sensitive to eye position. What happens is not exactly that I can't see the entire field of view, rather, when keeping my gaze fixed near the center of the field, slightest motion causes the field to darken noticebly, because one edge of my eye pupils has moved outside the beam of the exit pupil.I try to bear in mind that while it may be correct to say for example, "the exit pupil is x.x mm in diameter", that really there are many such exit pupils, each corresponding to a different direction of looking into the field of view. All these exit pupils cover a large area behind the eyepiece. For any given eyepiece position, eye roll angle, and exit pupil diameter, there will be a unique beam cutoff or vignetting. And even if the full beam off axis is received by the eye, there will be internal vignetting in most binoculars, which reduce the off axis exit pupils to a non circular shape, resulting in darkening of the field edge even under relatively bright viewing conditions. So for off axis viewing the effect is complicated. That's why I described only to the case of centerfield viewing, just to keep it simple.Thanks for releasing this exquisite Zeiss 15x60 for sale, hopefully into the hands of a hard user, rather than keeping it out of circulation as your beautiful but unused collectible.Ron</blockquote>

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