Camera shutter speed and chopper blades

Pretty cool trick- if you know how to change your camera's shutter speed.

Reminds me of a printing press stroboscope demo I watched nearly a decade ago..

A stroboscope is an instrument for observing moving bodies by making them visible intermittently and thereby giving them the optical illusion of being stationary. A stroboscope may operate by illuminating the object with brilliant flashes of light or by imposing an intermittent shutter between the viewer and the object.

For me, that little definition eventually led to the discovery of timing belts and how they use a similar kit for cars...