Rolling ball or globe effect is caused by the lack of pincushion distortion at the edges of the FOV. Field flattening lenses are used to produce sharp images with no distortion at the edges with the trade off being rolling ball distortion when panning with the binocular. The current trend in premium binoculars is to add just enough pincushion to prevent rolling ball. In the past the manufacturers have used too much pincushion also.
The new Swarovski SLC and Zeiss Victory HT offer a great compromise. No rolling ball but reduced pincushion over previous models.
You will only see rolling ball or globe effect distortion when panning. When panning the images entering or leaving the FOV appear to be moving faster than the images in the center of the FOV.
Its about a 50% chance that a user would be bothered by the rolling ball in the Swarovision series of binoculars. The 10x models seem to have a little less than the 8x models.
Timber:
The Swarovision EL binoculars are the best selling of
all the premium models on the market today. They are the
top of the Swarovski line. The SLC HD's are also well
regarded and either is a fine choice.
The rolling ball thing is greatly exaggerated, and few users will even notice. And most of those
bothered soon adapt and enjoy the great view.
You mention 50% of users will be bothered, and that is simply
not true. There is no way of knowing but it is minor under
10%. Otherwise how would these be selling and as popular as
they are.
I enjoy the view through mine.
