| Many folks, who have tried taking a picture of a spinning airplane propeller with their cellphone cameras, have been surprised by the results. The pictures show images of ghostly propeller blades, floating in the air, totally detached from the airplane. Here is how this happens: When a slow scanning digital camera (like the ones on many cellphone) captures an image, it does not expose all the pixels at the same time. Rather, it exposes and captures one row of the sensor at a time and then moves on to the next row. This simulated video demonstrates, in slow motion, how this results in images of floating detached propeller blades. |
