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Message: <blockquote data-quote="typo" data-source="post: 3147104" data-attributes="member: 83808">Kimmo,To correspond with optimum acuity at 2.5mm pupil diameter I should do my stopped down testing at 20mm for an 8x, 25mm for a 10x etc. I confess I've got lazy and usually only test 20mm irrespective of magnification. It's easier to relate the numbers to my perception of sharpness when comparing the same objective diameter. In this case it does reveal a flaw in this approach.At 20mm stopped down the Vanguard was 6.2" both barrels, the Eden 8.1" both and the Zen-Ray 6.3" left and 7.2" right barrel. In the Primes case normally the right would be paired with my weaker eye with no impact on overall performance. On a tripod I need to turn it upside down so the weaker lens is now matched with my stronger eye and that shows in the results above. You might note that for both the 10x I was able to get slightly better readings than the 20mm result would suggest. I presume the 25mm resolutions would correspond more directly.Perhaps I should point out that all three of these binoculars are pretty good and are in the range of effective resolution performance I've seen in certain alpha samples. These small differences I've referred to would be quite undetectable by the majority of users, particularly hand held. I've got a Wow! reaction for all three of them from experienced birders.David</blockquote>