When the camera’s frame rate matches the fast moving objects (such as helicopter rotors), a weird effect can occur and make the subject look like it’s levitating. Al Brooks noticed this when he was reviewing the security footage from his surveillance camera. And this time, it’s not a floating helicopter – it’s a floating bird. And while it’s amusing to see, it’s also a great illustration of the “wagon-wheel effect.”
This illusion occurs because the bird’s flapping wings perfectly aligned with the camera frame rate. In Al’s case, the frame rate was 20fps. Also, it has to do with the fast shutter speed, which is the reason why there’s no motion blur of the wings. When the fast shutter speed matches the adequate frame rate – we end up with the strange birdie that looks like it’s floating.
You can see more examples and a demonstration of this effect in the video below. It’s illustrated through the helicopter’s propellers, although, I must say – I find the bird much more amusing.