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Message: <blockquote data-quote="henry link" data-source="post: 410449" data-attributes="member: 6806">Thanks, Bawko, for the interesting post. I hope I can be forgiven if I take issue with your methods as a way of measuring the actual resolution of binoculars. I've performed these same kinds of measurements, both with and without boosted magnification. Every decent quality binocular I have tested (and even some pretty bad ones) has had actual resolution much too high to be seen without boosted magnification. What I see looking directly at a resolution chart through binoculars is simply my eyesight acuity (at a given moment) divided by the binocular's magnification. I am certain that using your chart and boosting the magnification of each binocular to 40X-60X would show the actual resolution of all but the cheapies to be better than 3" and some (like the 7x42 Leica) probably better than 2". I think the differences in resolution you are finding without boosted magnification result either from very serious optical defects in some of the binoculars or more likely are the natural variations that occur when straining to see tiny details at the limit of visual acuity. For reference, 20/20 vision is supposed to correspond to 60" of resolution and the best human eyesight is about twice that good. Looking at your results I think your acuity probably falls between 45" and 50" on your chart, which is about the same as mine, so you could expect to see around 7" in almost any 7X binocular, 6" in an 8X, 5" in a 10X, etc.Putting aside acuity, another problem with this method is that it can only allow you to measure that part of the binocular's exit pupil equal to or smaller than the eye's entrance pupil. If your eye is open to 4mm when using your test set up, then you are looking through only the central 28mm of your 7x42 Leica Trinovid's objective, so the full resolution of the objective could not be seen even if your acuity allowed it. Under the same lighting conditions small binoculars with 2.5mm exit pupils effectively shut down your eye to 2.5mm which reduces the aberrations of the eye itself. That might partially explain why your 10x25's look so good in the tests. BTW, I've found that a difference in vertical and horizontal resolution usually indicates misaligned optics or astigmatism. Boosting magnification would not be very difficult in your test set up. You can simply use one barrel of one of your small binoculars behind the eyepiece of the one being tested. You could also easily make an artificial star (very tiny holes in aluminum foil in front of a light bulb) which would be good enough to identify defects in the binoculars you are testing. Once again, thanks for the interesting post. I hope you don't mind the unsolicited advice and suggestions. Henry</blockquote>

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