The Sony HDR-AS30V camera lens has a view angle of 120° or 170°, achieved by internal image processing rather than mechanical lens adjustments. For most action-camera purposes you don’t care about fisheye distortion, but sometimes a more rectilinear picture will look better, in which case the GIMP’s Lens Distortion filter comes in handy.
A still image at 120°, which doesn’t look all that bad, really:
Main=-25 gives this:
A frame captured from video at 170°, with the overhead wires hanging upward:
Zoom=+8 flattens them enough to be acceptable:
The main effect of the
Zoom parameter seems to be discarding the severely distorted remnants around the edges of the corrected 170° view. Sometimes, those pixels around the edges can be very, very important, so I’d rather make that decision after the fact.