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Old Saturday 30th July 2011, 21:09   #14
henry link
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Join Date: Feb 2004
Location: north carolina
Posts: 4,093
I think I've done all the testing Of the Dakota Elite 8x32 I want to do, so here's a short review.

First the measured resolution is respectable for a binocular, about 5 arcsec in the left side and 5.5 in the right. A perfect 32mm optic would measure about 3.6 arcsec, but even some 32mm alpha binoculars don't do any better than 5. What appears to limit the resolution here is sloppy assembly. Both sides show astigmatism and coma in a 64x star test and the left side has an odd aberration I haven't seen before, which may be a turned down edge, but the underlying spherical aberration is actually quite low. I was able to eliminate most of the astigmatism (and the possible turned down edge) by stopping down the binocular to 24mm, which resulted in a pretty good looking star test except for the coma. That and the forgiveness of low magnification explain why the center field image looks quite sharp in daylight. Off-axis sharpness is good enough, not too different from a Zeiss 8x42 FL, maybe a little worse. Distortion is very similar to the Swarovski 8.5x42 SV. It looks like normal pincushion until about 75% from the center, then it reverses so the last 5 degrees or so are free of rectilinear distortion, but show angular magnification distortion which compresses objects at the field edge.

The two weakest areas of performance are light transmission and resistance to veiling glare. I'm including two photos that show the nature of the problems. The left photo shows the reflection of a light bulb returning from the some of the lenses and prisms of the Dakota (left) and a Zeiss 8x42 FL (right). The two largest reflections in each case come from the prisms. In the Dakota one of those is uncoated (large white reflection) and the blue one is bright enough to be a single layer coating. There is probably one other uncoated prism surface I wasn't able to see. The result is overall light transmission that I found slightly dimmer than an old Porro with single layer coating (Nikon 8x30 E), perhaps 75% or less. This isn't the first time I've seen this kind of corner cutting in an inexpensive Chinese binocular. I don't see much point in speculating over possible refinements to the coatings when the OEM doesn't even coat interior surfaces when they can get by with it.

The other photo, made through the eyepiece, shows the source of veiling glare, a bright unbaffled spacer behind or between objective elements, which looks like a thin crescent at the edge of the objective. In the binocular FOV the glare shows as a big fuzzy crescent of light filling about half of the field opposite a bright light source like the sun when the binocular is pointed within about 40 degrees of the light. This can be minimized by moving the binoculars laterally in front of the eyes a little to line up the prism aperture so that it covers the shiny side of the objective.

Eye relief is a bit short for eyeglass wearers. I measured about 11mm from the rubber eyecup in the down position, about 15mm from the glass. Happily, the aperture is a full 32mm, the magnification appears to really be 8x and the FOV appears to be about as specified.

Overall, I think this is a pretty decent pair of binoculars. Mine will probably go to a nephew.
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Last edited by henry link : Saturday 30th July 2011 at 23:33.
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