Image Stabilization: Beating Jello
Modern camera drones are quite good at capturing aerial video, but they are still essentially cameras mounted on platforms that can move around violently during flight. In Chapter 1, we talked about the importance of vibration isolation, which reduces the amount of high-frequency shaking that reaches the camera sensor. Obviously, shaking a camera while recording video is not going to lead to great results, and even vibration that is too subtle for the human eye to see can lead to artifacts called jello that will ruin your video (FIGURE 4.2). To see examples of jello in aerial drone videos, do a YouTube search for drone jello.
FIGURE 4.2 An example of “jello” in an image captured from a vibrating camera
Luckily, good camera drones ship with effective vibration dampeners pre-installed and propellers that are pre-balanced from the factory. When flying in calm conditions, you should not see any jello in video, and in most cases, jello is caused by damaged propellers or problems resulting from a previous crash. If you see jello, inspect your motors to make sure they are not damaged, swap out or balance propellers, and make sure vibration dampeners are properly installed.
If you continue to see jello in your video even with a perfectly balanced camera drone, the vibration may result from environmental factors like wind. Gimbals and vibration dampeners are designed to withstand a certain amount of wind before they start to vibrate; the strength of a motor is a direct trade-off with weight, and manufacturers always have to strike a balance between stabilization strength and total weight.
In my own anecdotal experience, I’ve found that camera drones like the DJI Phantom 3 will not exhibit jello at maximum speed if there isn’t much wind. However, if the wind is blowing strongly (say, at 25 MPH or higher), a Phantom 3 may exhibit jello in its video if it is flying against the wind, both forward and backward. This is a bit confusing because a Phantom that is stationary against 35 MPH winds should be subjected to the same forces as a Phantom that is flying at 35 MPH in windless conditions. This confusion reflects how complex camera drone systems really are, and jello is just one of the potential issues that can occur if your camera drone is not properly tuned, either by a manufacturer or by a custom builder.