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Message: <blockquote data-quote="elkcub" data-source="post: 1262386" data-attributes="member: 14473">EdZ,Thanks for the response.  At least I'm in the right ballpark.Keeping in mind that I'm still trying to understand the issues:1.  For the single observer looking at binoculars of different resolution, would they max out at the same booster power?  Perhaps I don't understand what you mean by "... At the same power limit they show very different results."  2.  For two observers with the same acuity showing different results comparing different quality binoculars, my first thought is that matching visual acuity between individuals is difficult.  For example, in the lab I would determine if the observers produce the same results with a standard reference binocular under controlled observing conditions.  If not, they are not matched regardless of Snellen acuity.    3.  This scenario is quite complicated, but I will make this observation.  Using standard resolution charts it is possible to produce pseudo-resolution due to the manner in which CA operates in the combined instrument and eye.  In fact, this little nasty is always a potential limitation.  Basically, the instrument, booster, and eye are coherently coupled, so CA (and other aberrations) can reinforce or cancel each other.  This depends on the particulars.  When asked to make a detection, the observer can respond to CA spilling between grid lines even though he can't actually resolve them.  So, we get down to a basic problem of definitions: what is instrument resolution, and what is visual acuity?  (I can provide a reference if interested.)  Just some thoughts.  Ed</blockquote>

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