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Message: <blockquote data-quote="henry link" data-source="post: 3667665" data-attributes="member: 6806">The link does seem to imply that Angular Magnification Distortion and Barrel Distortion are the same thing, but as Jack said, that is not correct. However, I'm finding that explaining or illustrating the relationship between the rectilinear distortions and AMD is not so easy. The figure below is the best I've come up with.The horizontal line represents rectilinear distortion. Barrel increases toward the left and Pincushion toward the right, with the point of zero rectilinear distortion at the intersection of the vertical and horizontal lines. AMD is represented by the dashed diagonal line. Positive AMD increases toward the upper left and negative toward the lower right with the zero point for AMD occurring at the intersection of the dashed line and horizontal line along the Pincushion part of the line. Notice that there is substantial AMD at the zero point for rectilinear distortion and substantial Pincushion at the zero point for AMD. One increases as the other decreases. That is why a distortion free field is not possible. With binoculars we are mostly concerned with the little triangle made by the two intersections of the dashed and solid lines and the intersection of the the two solid lines. The distortions of most binoculars fall somewhere along the pincushion line and the AMD line of that triangle. Less Pincushion means more positive AMD and the changeover to Barrel just means even more positive AMD. More pincushion beyond the point of zero AMD changes the AMD from positive to negative (shapes at the field edge become radially stretched instead of squashed). I've only seen one example of a binocular (Leica 8x42 Ultravid) with enough Pincushion for negative AMD and only one where I suspected there was a small amount of Barrel at the field edge (Zeiss 8x42 SF).</blockquote>

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