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Message: <blockquote data-quote="kabsetz" data-source="post: 3161259" data-attributes="member: 10167">Field curvature and rolling ball are interesting in that opinions vary so widely on them. I did Holger's k-test, and was most closely in his group B, which was seemingly one of the most normal ways of reacting to AMD and RB.I see some rolling ball in my Nikon 10x42 SE, but it does not bother me. I see virtually no RB in my 10x42 Canon, but that may be partly due to having used it so much over the last 7-8 years. But when I deliberately try to see angular magnification distortion in it (radial dimensions collapsing towards the very edge of the field) I can see very moderate amounts but not much by any means. A week ago I had the Zeiss SF 8x42 and a brand new Swaro SV 8.5x42 for testing for a few days, and spent a fair amount of time visually evaluating their viewing properties. Now, contrary to what the graph on Holger's webpages would suggest, where the SF should be more or less at the sweet spot for distortion and AMD, to my eyes it had significantly more RB and more pronounced AMD than the SV, which had a little more than the Canon. I would judge that the SV would be for me easy to get accustomed to, the Zeiss more difficult but very likely possible. The reason why I find the Zeiss acceptable in use despite relatively high AMD is that the field of view is very wide and the effects of AMD are only visible in the last 10-15% of the field off axis. Now, in normal viewing and panning I tend to have my eyes more or less viewing along the central third or so of the view field. Thus the potentially objectionable stuff happens in the peripheral vision area and is hardly a problem.One interesting thought came to me when thinking about flat field technology and the design compromises involved. This comes from looking at the cutaway views of the eyepieces of the Canon 10x42 and the SF, as well as inspecting the eyepiece of the SV with the eyecup removed. What I mean that in the Canon design, the 23mm wide eye lens is not the largest diameter lens in the system by a long shot. The third lens in is much wider, and the twist-out eyecup diameter is 44mm. In the SF (25mm eye lens, 39mm eyecup diameter) and SV (24mm eye lens, 40mm eyecup diameter) the eye lens is about as wide as it can be given the overall external diameter of the eyepiece inside the extendable and removable eyecup cylinder.It may be that the edge distortion characteristics in the SF, and to a lesser degree in the SV, are at least partially what they are in order to allow for an eyepiece that fits within certain physical dimensions while providing a wide enough true field. Hopefully the dismal Canon eyecups could be designed slimmer by some clever engineering, but partly they seem to so huge in order to accommodate that large third lens.Kimmo</blockquote>

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