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Message: <blockquote data-quote="kabsetz" data-source="post: 266022" data-attributes="member: 10167">I liked Henry's explanation about the image scale illusion between porros and roofs. When I was testing 10x binoculars, I was bothered enough by the apparent magnification difference between the Zeiss FL and Nikon SE that I went and did a comparative magnification measurement with them to determine whether the SE really had less magnification. The result was that it actually had slightly more, by about 2.2 percent. I measured this by viewing a ruler set at ten meters (target to objective lens) with both binoculars fixed with a 3x booster, and by measuring the total field width in millimeters visible through the booster.To test Henry's explanation, one could probably devise a test setup where one would use a simple two-mirror periscope for one eye to widen one's naked eye interpupillary distance and see whether this makes objects look smaller compared to the immediate reference of viewing the same objects without the periscope. If anyone is inspired to try this, please post the results.Kimmo</blockquote>