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Message: <blockquote data-quote="kabsetz" data-source="post: 3143613" data-attributes="member: 10167">Some degree of observer bias is unavoidable, but both David and myself have quite a bit of experience by now of viewing bar targets, and since the test we are contemplating does not really have to be dead serious, I don't think it is going to be too much of a problem.If you try to do binocular resolution testing with two-eyed viewing at close ranges, parallax error becomes an issue, less so for roof-prism or reverse porros, and much more so for traditional wide porroprism binoculars. Even ten meters is a bit short for the latter, but with good ones such as the 10x42 SE it works pretty well.Kimmo</blockquote>