I bought the Helios naturesport plus 10x50WA this summer as backup binoculars. My main binos are Zeiss 8x30 B roofs and the reason for the purchase was to have backup binoculars with a larger aperture, also suitable for occasional stargazing, and because I wanted to try out 10x magnification for birding.
At first sight they seemed pretty good. Good prisms and good coatings result in a bright and contrasty image. Central sharpness is decent, field of view is excellent, eye relief is excellent. Build quality and flare resistance are IMO quite acceptable for the price level. Sweet spot seemed already smallish at purchase, but my thoughts at that time were: hey I only need the large field for noticing that there is something there, and then use the center for taking a good look at it.
However after a couple of days in the field my initial enthousiasm cooled. There is quite a bit of CA color fringing, but thats only a showstopper in specific circumstances. But unfortunately after a couple of days of testing and adjusting I had to conclude that the eyepieces are no good. The sweet spot with good sharpness is just too small and its position varies with eye placement. This means that you have to adjust interpupil distance extremely precise, otherwise the sweet spots of left and right are not in the same place. Even then you have to be very precise about how you bring the binoculars to your eyes.
A smaller problem are the eyecups. They are largish and of the rotating type but have no intermediate positions. With my old glassed they were OK, although the up position was a slightly too far out withouth glasses and my "western" nose and eyebrows. But since then I bought new, much closer fitting glasses and now I have too much eyerelief with the eyecups down.
So my conclusion is that these binoculars offer good value for money if you put them on a tripod and have a couple of minutes to take a good look at your subject, but for birding they take too much attention and distract too much. (Someone with younger, more adaptable eyes might have a different view)
IMO These binoculars would be pretty good for birding if they were 'upgraded' to more simple, but easier to use Kellner eyepieces with standard folding rubber eyecups. Ofcourse that would mean a smaller field of view and less eyerelief and lesser specs on paper. And I wouldn't have bought them, because of the not so close fitting glasses I was wearing back then.
Still these binoculars were usefull to me, if only because it didn't cost me too much to find out that 10x is not the optimum for me personally and that I will stick to 8x or 7x when I eventually replace my main binoculars.
Erwin
