BirdForum is the net's largest birding community dedicated to wild birds and birding, and is absolutely FREE!

Register for an account to take part in lively discussions in the forum, post your pictures in the gallery and more.

Reply to thread

Message: <blockquote data-quote="Vespobuteo" data-source="post: 3425310" data-attributes="member: 120830">As I understand it, stopping down the binocular objective means using the "best" part of the objective lens (lowest aberrations in the center). So I guess that it will not be equal to using a smaller objective bin?With a stopped-down bin set-up I think it might be difficult to show that the cause of potential increased perceived sharpness is the smaller exit pupil rather than using the central part of the objective. Dawes limit (R = 4.56/D) would also suggest that the max. theoretical resolution will decrease stopped down (smaller D), not necessarily a good thing?A slight brightness loss also can make things look more "contrasty" if the current light is good.So I just wonder what the explanatory model would be for a smaller exit pupil bin as a 10x32 would look sharper than a 10x42? Angle of incidence on the cornea? Circular area of the cornea used? wouldn't it be identical due to different usage distances? And wouldn't it be more of a question of the eye relief? And also the quality and aberrations of the image disc produced by the binocular itself?Current eye pupil size will also have an effect on the max sharpness the eye could reach I guess. With a smaller eye pupil it will be sharper. A 42mm bin will gather more photons, so total amount of photons will be larger with a larger bin, photon density might be not. A 32mm bin with less glass in the light path could have better transmission on the other hand. Any effect on the pupil size there? Definitely in low light conditions, where the pupil size exceeds the EP, though any potential exit pupil effect on sharpness would be most relevant in daylight.Just wondering..:smoke:</blockquote>

Verification