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Message: <blockquote data-quote="henry link" data-source="post: 3574382" data-attributes="member: 6806">Well guys, we all know there’s a never-ending parade of different individuals praising and condemning the very same binocular. The sad fact is that the usual hand held evaluations at normal magnification occur in an ever shifting borderland where binoculars with unknown aberration levels and possible sample defects meet testing methods that are inherently compromised, uncontrolled and unrepeatable. Is there any wonder that the basic optical characteristics of the instrument are so difficult to establish that way? I’ll happily admit that I’ve deliberately searched for testing techniques that are controlled and repeatable, and will prevent my particular eyesight profile from unduly influencing the results. How can we hope to understand the complex interactions of individual brains and eyes with particular binoculars if we don’t first accurately establish the optical characteristics of the thing our eyes and brains are interacting with?On the specific question of the usefulness of the USAF 1951 chart, I agree that it isn’t very good for visual resolution testing of binoculars at normal magnification. The lines are too short and the elements crammed too closely together for reliable readings when the apparent size of line pairs becomes very tiny. I think the NBS 1963 Resolution Chart would be better for that purpose. It has longer lines and wider separations between groups of line pairs. I’d like to have one, but I would want a vapor deposited glass slide like the USAF 1951 I use now and those are quite expensive. Henry</blockquote>

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