I don't have one myself, but every video I've seen from a GoPro has used a
wide-angle lens that is moderately fisheye - meaning that the horizon and
other straight lines bend unless they go through the center of the lens. I
guess it's really just plain old barrel distortion.
Would it have been possible for GoPro to use a lens with the same 127-
degree field of view, but rectilinear instead of fisheye? If it is possible,
would it have been prohibitively expensive for a camera of this price range?
Well, obviously I don't know anything about lens design, but to my eye the
fisheye effect, even though modest, is a "con" for this camera, and just
wondered if a different approach might have been possible, or might be
possible, without losing the wide angle field of view.