The horizon is below the centre point of the fish eye lens and therefore is distorted in the opposite direction to the curve. This is why it looks flat. Balloon footage with fish eye lenses can only prove anything if the horizon crosses the centre point.
You can see that it's a fish eye lens if you watch the rest of the footage...
Of course it's a fish eye lens. Look at this frame...
Either that's lens distortion or the horizon is curving UP at the edges.
And look at the distortion of that radio mast in the background at launch...
It's curved to the left when it's on the right hand side of the frame...
http://i.imgur.com/JWDUKZU.jpg
And it's curved to the right when it's on the left hand side of the frame.
http://i.imgur.com/rr0mlzx.jpg
Do you still think this isn't a fish eye lens?
I know what video you were talking about. That was the launch of the balloon you used in your video. Your clip was taken from around part 11. You can watch all of the raw footage here...
https://www.youtube.com/playlist?list=PLWnGN1-KTMqwrnWyItEaa61M14kN-riwc
So definitely fisheye.
Thank you for posting yet another video with a curve...
