:lol:Go Go gadget marketing!
Wha... how... ?
FTFYRotor blades syncing with the framerates of the camera,probablyof course.
Clearly they don't have kids.
Also, who are you to decide what people do or do not need?
FTFY
The Kamov-helos are famous for their coaxial contra-rotating rotors, thus making the rear rotor unnecessary since there is no yaw momentum. In that Video/GIF the upper rotor rotates with almost exactly a multiple of the shutterspeed of the camera. That's why the picture is only exposed when the rotor is in the same position.