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Message: <blockquote data-quote="elkcub" data-source="post: 1310783" data-attributes="member: 14473">I don't understand this, but thanks for confirming my observation: he used the images twice.  Until this dawned on me I thought the first pair contrasted a roof with a porro, and the second pair contrasted an uncorrected roof with a corrected one.  But identical pictures can't be used for both purposes (at least not logically.)  Coupling this with his reference to a seminal study of chickens adapting to image inversion, now an urban legend*, and the dubious statement: my inclination is to think he was just pushing Zeiss roofs.  The question on the table, however, was what evidence is there that P-coating changes either the star-test image or the line seen through the objective?  It may have these effects, but I don't think S. Ingraham's article provides much insight.  Again, just my opinion.  EdPS.  *My annoyance is not his reference to chicken studies, exactly, but his lack of understanding that they were done to verify Stratton's strong conclusions about early experience determining visual perceptual orientation.</blockquote>