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老外对EII和bd2的两张镜后图做了点分析，这老外还是比较细致的。
I've had some fun with the images attached to range's post #329. Ideally they could tell us quite a bit about the comparative magnifications, AFOV and distortion characteristics of the binoculars, but that is somewhat qualified here because we don't know what kind or amount of distortion is being added or subtracted by the camera lens. Still, since the camera lens affects both to about the same degree a few things can be reasonably deduced.
Firstly, the center field magnifications of the two binoculars are nearly identical, so we know that the Kowa's smaller real field is not caused by higher real magnification.
Secondly, there's no doubt that the Nikon has much more pincushion distortion and therefore much less angular magnification distortion than Kowa. Notice that the wooden slat at the bottom of the image shows pincushion distortion in the Nikon image in contrast to slight barrel distortion in the Kowa. Also notice the difference in shape of the window at the extreme left of the image. It's more horizontally compressed in the Kowa image from higher angular magnification distortion. That, combined with the Kowa's smaller real FOV, give it a substantially smaller true AFOV compared to the Nikon. If we assume that the field circles in the photos are the eyepiece field stops of the binoculars then by simply measuring and comparing the diameters of the circles we find that the true AFOV of the Kowa is about 62.4o compared to the 66.5o true AFOV I've measured for the Nikon EII.
Looks like I'll get a chance in a couple of weeks to test a BDII 10x42 XD that a friend has decided to purchase. I should be able to provide some measurements and hopefully some explanations of the subjective impressions we've had so far. |
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老弟最近可好？若有机会来京可一定得告诉我，我还欠您一顿酒啊
