When I fly my racing quad I use a GoPro camera on it, and on most of my videos, I have some wavy lines running on the outside of the frame. Is there any way to get rid of these?—Luis Gonzalez, Sun City, CA
Answer:
What you might be experiencing is the effects of rolling shutter, also called “jello” or “prop blur.” Jello is what happens from the high vibration on the quad; the video looks as if it were shot through clear Jello. Prop blur refers to the artifacts that occur when filming a propeller or rotor using a stock camera (like the GoPro) that has a fast shutter speed. The propeller appears to be fragmented and is not what we see in real life.
Because the shutter speed on GoPro cameras is mostly automatic, bright sunlight will increase the shutter speed. Adding an ND (neutral density) filter slows down the automatic shutter speed by reducing the amount of light that the camera detects. Slowing down the shutter speed will reduce or even eliminate these artifacts and significantly reduce the jello effect. Darker ND filters, such as an ND8, should be used on brighter days. Less-dark ND filters can be used on overcast, less-bright days or when the sun is sinking in the west; in this case, you would use an ND4. Because of this, you will have to try out different densities of ND filters. You will most likely have to use one ND filter strength in the morning, a different one in the afternoon, and yet another later in the day.
