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  1. H

    Review of Kowa BD II 6.5x32 XD

    Thanks Mike. I just noticed that the AFOV of the 6.5x32 should be considerable smaller than the 10x42. I say "should be" because Kowa's spec for the 10x42 was so far off. Anyway, a smaller AFOV could also partly explain lower AMD at the field edge in the 6.5x32 because there is just less room...
  2. H

    Review of Kowa BD II 6.5x32 XD

    From the observations and photos posted so far I would say the 6.5x32 has the same mustache distortion profile as the 10x42, but the swing between the two rectilinear distortions is less extreme in the 6.5x32. From my photo of the blinds you can see that the 10x42 develops pretty strong...
  3. H

    Review of Kowa BD II 6.5x32 XD

    Thanks Canip, Torview and Mike for your efforts! Torview's image does show a more complete view of the mustache distortion pattern, but I'm curious about the prism edges that visibly intrude inside what I assume to be the eyepiece field stop. Notice that the prism edges in my photo of the 10x42...
  4. H

    Review of Kowa BD II 6.5x32 XD

    Hi Canip, I think the camera was too far from the front of the binocular. It needs to be close enough so that the camera can see the sharp field stop of the eyepiece. The fuzzy opening in your photo appears to be an out of focus internal stop, probably a prism aperture. I use a DSLR with the...
  5. H

    Review of Kowa BD II 6.5x32 XD

    That's very surprising to me, Gijs. As you know it's impossible for a binocular to have no distortion. The designer has to choose between more pincushion with less angular magnification distortion, more AMD with less pincushion or the mixture of the two called "mustache" distortion. One would...
  6. H

    Review of Kowa BD II 6.5x32 XD

    Gijs, I think you will be able to see the distortion if you examine a 5 cm circle from about 8 meters away (or any combination of circle size and distance that results in a circle that subtends around 2-4ยบ of AFOV). Move the circle from the field center to the edge. In the Kowa and other...
  7. H

    Review of Kowa BD II 6.5x32 XD

    Gijs, I think Canip is talking about distortion rather than field curvature. I described and photographed the distortion profile of the 10x42 in this thread: https://www.birdforum.net/showthread.php?t=384387 Henry
  8. H

    Review of Kowa BD II 6.5x32 XD

    Your method is just fine to show that the prism edges extend into the exit pupil. Since the prism edges are glass we can reasonably assume that they create a bright reflection visible to the eye if light coming from the objective strikes them at just the right angle and is reflected back toward...
  9. H

    Review of Kowa BD II 6.5x32 XD

    I've seen this in binoculars with undersized prisms. It can vary a little from unit to unit if the prisms are mounted a bit off center. However, viewing through the front doesn't accurately predict whether these prism edges impinge on the exit pupil. Try using a magnifier to examine the interior...
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