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Message: <blockquote data-quote="ronh" data-source="post: 1282005" data-attributes="member: 55514">Ron,What a thorough reply, just when I was afraid you might have given up on me. The use of the collimator is very interesting. And it is fascinating to think that MTFs are actually measurable. If a perfect f/4 optic goes to 560 lp/mm in the focal plane, what fine granularity a CCD array must have to sense the resolving powec, to actually map out not just the peaks and valleys, but a fair representation of a sinusoid! It's all very impressive. Thanks especially for saying that it wasn't clear from the paper how they made the measurement. That single remark has, perhaps unjustifiably, made me feel a bit less stupid!This has been a good learning experience. I am not an optics pro. Lord knows, I do not, like you, have a decent lens kit! To you, and the other guys too, I apologize for "hammering" on this issue, perhaps too hard for a web forum, where technical discussions are difficult and should be limited. But I love this stuff.You have been kind, and are free to go now!Ronh</blockquote>