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Message: <blockquote data-quote="typo" data-source="post: 3439910" data-attributes="member: 83808">Ed,Using a roof for usually less than 5 minutes at a time is going to be very different hours of serveilance with a porro. Bescides those two, I've probably only seen a handfull that felt like they were giving me immediate eyestrain out of many hundreds I've tried.I've not found the notes I made at the time, but it my memory serves me right, out of 5 roofs I tried with this method, the maximums I got just under half a degree (~25 arcminutes) convergence. 1.3° (78') divergence and 2° (120') dipvergence. Given the crude method, the dipvergence would be least reliable. That miltary spec has no tolerance for convergence, but we've been told convergence was deliberately employed for an Avimo British/NATO binocular. My divergence value is about two and a half time the military max and I accept my dipvergence figure may be high. The SPIE field guide says civilian binoculars may exceed those limits so I see nothing particularly contradictory in the values..The point I was making about those two I received with obvious dipvergence was that, for me the centre performance was unaffected as far as determine, and although I could easily see the misalignment, I could comfortable ignore it as well. You may well differ, but if my test is at all representative of mid range binoculars ( and I accept it may not be) then most users would appear to be quite tollerant.David</blockquote>