A frame from an video, shot with an iPhone4 from a moving car.
At first I thought these skewing artefacts were just something you had to put up with when using cheap digital video (the above is a single frame from a video shot on an iPhone4 from a moving car), but then I discovered that it’s also a problem with still images:
It’s caused by an effect known as rolling shutter, which is common to inexpensive CMOS image sensors such as the one in my phone. This is pretty shitty really, because you’ll get (usually unwanted) effects in pretty much any shot involving substantial movement. Although sometimes it delivers some truly interesting results, such as when you film something spinning very fast, like a propellor: