Home movies, often filmed with a cell phone camera, also tend to cause motion sickness in those who view them. The person holding the cell phone or other camera usually is unaware of this as the recording is being made since the sense of motion seems to match the motion seen through the camera's viewfinder. Those who view the film afterward only see the movement, which may be considerable, without any sense of motion. Using the zoom function seems to contribute to motion sickness as well since zooming is not a normal function of the eye. The use of a tripod or a camera or cell phone with image stabilization while filming can reduce this effect.