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Message: <blockquote data-quote="ronh" data-source="post: 1280415" data-attributes="member: 55514">Ron,Thank you very much. So the rules are 1) both black and white stripes count as lines, and 2) measurements are of period, for example, center to center.In Konrad's paper, the binocular whose prism has the best glass, and the chosen single layer coating, has a contrast at 40 lp/mm that has fallen to 25% of maximum. Now, I know that 40 lp/mm means that black stripes are centered 1/20 mm apart. In the f/4, 8x42 that I assumed earlier, 1/20 mm in focal plane, viewed through a 21mm eyepiece, gives black stripes separated by 8 arcmin. That's four stripes across the moon to the naked eye, is all. This separation is easy to see, and and degradation in contrast to 1/4 that of the object sounds really bad.The link of post #14 (3/4 down the page) shows that this frequency, which is 7.5 cycles per degree, is in fact at the very peak of the eye's performance. If the contrast was suffering badly at this frequency, it should be obvious at a glance.Henry has made two reasonable arguments that there may be no inconsistency between the plots in the paper and visual experience. One, the binocular and prism both would perform better if the beam were stopped down by daytime pupil of the eye. True enough. But, I'm often out in dusk conditions when my eye must be open to 4-5mm (my eyes open to 6+mm maximum), surely getting a majority of the 8x42's beam, and my binocular still seems to be working very well. Two, the paper is not upfront about the objective lens. But it does say 42mm is the maximum for the Schmidt-Pechan, and what they had laying around was Swarovski binocular objectives. If this hunch is correct, the degree of the mystery does depend on the choice of objective, but not critically. Sorry for the rant. I can't blame anybody for not wanting to wade through such a thicket. But, I still cannot reconcile the plots with visual experience. Ron</blockquote>

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