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Message: <blockquote data-quote="OPTIC_NUT" data-source="post: 3172025" data-attributes="member: 121951">Awesome data, Henry!That's for a single objective lens, though, correct?Most optical systems play various aberrations off against each other..so things aren't quite that bad.  The field lens and/or the flattener before it bear most of that load.  Still, those compensations have theirpatterns as well (not the same periodicity in that graph), thus the phenomena like the "fuzzy donut", and thesevere deterioration of most binoculars at the edge. If we only had 2 elements, things would be bad indeed,and the eyepiece element would actually multiply theerrors you show.   The rest is adding things to wrestle with the beast.Note that a test with many many line pairs is much more challenging than detecting a single 'half pair', like the edge of a beak against the snow.The many line pairs model fills in from two peaks instead of one,so the contrast is a lot less.  In a nutshell, most object you see have dark|bright edges, not the dark|bright|dark|bright...etc of the tests.(so everyone typically sees with more sharpness for most things).</blockquote>