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Message: <blockquote data-quote="looksharp65" data-source="post: 3622880" data-attributes="member: 83771">Hi Omid!I haven't claimed that the porro's wider spaced objectives increases the binocular's FOV, but the parallax difference is significant at medium and close distance which enhances the 3D perception.Your drawing of the increased FOV resulting from diverging optical axises looks correct.In theory, the common, almond-shaped central part of the FOV could coincide fairly well with the human FOV. However, the binocular part of the human FOV covers about 120 degrees horizontally.If the binoculars in your examples have wide angle eyepieces, each of them would cover say 75 degrees (apparent field of view). This means that the fieldstops by default limits the usable FOV by at least 20 degrees towards each side.Any divergence of the tubes will further shrink the common (shared) area and expand the monocular area. I assume your drawing is exaggerated to show the effect more clearly, but only a third of the FOV is shared there.If we take into account that the eyes ideally scan a scene and prefer to roam freely, it's apparent that they will meet the fieldstops earlier than in an ordinary binocular.The user would probably react with turning the binoculars further towards the point of interest, hence losing what's happening at the other end of the FOV and losing the very reason for using this invention.This said, if the divergence is kept very low, and the optical challenges could be met, it might work as you described, with only minor inconvenience of the types in my objections. It would take eyepieces with huge AFsOV to compensate the loss of the common FOV as much as possible, and such binoculars already make a great job. I'm mostly thinking about the Nikon EII series, but wide angle constructions from the seventies with "up to and above" 80 degrees AFOV are also interesting in this context.Regards,//LEdit: added a drawing that Ed originally provided me in another discussion.</blockquote>

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