[Arve]

The point here is that the rotation is done by the OS, in software, so the screen is still painting from the physical left-to-right and top-to-bottom. This is something you'll never notice with the naked eye, but their camera uses a staggering 2700fps. This means that a full repaint of the screen - assuming 60Hz refresh happens in 45 frames. Those 45 frames, played back at 30 fps means that the full repaint takes a second and a half, leaving you with the ability to see the individual lines being (re)painted.