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Message: <blockquote data-quote="elkcub" data-source="post: 3174364" data-attributes="member: 14473">Well guys, I think you’ve put up a perfect tag-team defense of star-testing based on Suiter’s “Manual for Optical Evaluation and Adjustment” and your own extensive experience.  Please recall that in post #39 I appended Warren Smith’s statement about the subject being for experts, which you certainly are.  My own interest, however, is not “optical evaluation and adjustment.”  In this instance, it is to address the relationship between perceived “resolution” and “sharpness,” which is the subject of the thread.  In my view that has very little if anything to do with locating optical flaws in the objective, or binocular as a whole, and everything to do with the characteristics of the image that appears on the retina at the end of the optical train.  I am referring to the ideal image intended by the manufacturer, assuming that the instrument is perfectly made and fully adjusted.  For their part, vision scientists agree that the MTF of the retinal image is essential for judging image quality, but I don't think that, in itself, address questions about perceived resolution and sharpness, allowing that those terms are defined in a way that can be measured experimentally.  In any event, I don't see how the question can be approached without consideration of the eye's optical contributions to the image on the one hand, and its perceptual processing mechanisms on the other.  (The eye is an anatomical extension of the brain.)  Broadly speaking, that's the subject of Mouroulis' book, but, unfortunately, those who are only interested in assessing the stand-alone optical quality of telescopes or binoculars won't be any more interested in it than, let's say, the importance of the visual sensitivity function for understanding binocular brightness.  Dismissing the whole subject as similar to "... assertions in promotional material for binoculars and spotting scopes," though, is almost funny.   I think Ron characterized it very well a few years ago by saying that he wasn't interested in anything beyond the instrument's exit pupil.  So, I guess I'm just a creature who lives beyond the eye's entry pupil. Anyway, no offense intended and I still have great admiration for you all.  :flowers: Ed</blockquote>

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