What is a rolling shutter?
Sensors can come with either a global shutter or a rolling shutter. With a global shutter, the entire image is exposed simultaneously. If we were to slow down the process, the exposing of an image would look like a fade in.
On the other hand, a rolling shutter exposes different parts of the frame at different points in time. If you were to slow down the process, the exposure of the image would look like a linear wipe, similar to a garage door retracting up a down. The camera sensor begins at the top of the frame and becomes light sensitive one line at a time and rolls down in this process until the entire frame is exposed.
What is the jello effect?
DSLRs come equipped with rolling shutters. Usually the rolling shutter process is quick enough that we wouldn’t even notice it. But issues arise when you do quick pans or have extremely fast moving subjects like an airplane propeller. Quick pans make the image wobble like jello (hence the name jello effect), and images can become skewed with straight lines becoming distorted.
In the video below you can see that the rolling shutter makes it appear as if the propeller blade is flying off.
So why do cameras have rolling shutters if they produce jello effects? Basically because rolling shutters are a lot less expensive than global shutters.
How to overcome negative effects of rolling shutter?
- Slow down.
Shoot at slower shutter speeds so the motion blur can mask the rolling shutter effects. Secondly, rolling shutter effects happen when you’re moving quickly, for example whipping your pans. Slow down your pans. Whipping your shots just makes your audience nauseous anyway.
- Remove it or blur it.
The obvious answer is if the jello effect is occurring in a subject that is not the primary focus then recompose the shot so the items is not within the scene. For example, if that propeller blade is not necessary, move your camera around so the viewer can no longer see that propeller. If the skew is occurring in something in the background, you can attempt to blur it out by changing your depth of field.
- Fix it in post.
There are some plugins and software available to help correct the footage.
Study break: Vegans can’t eat jello. The gelatin is made of collagen from cattle bones, hides, and pork skin which are ground up and soaked in acid or lime. The mixture is boiled then filtered repeatedly to extract the collagen which is then dried and ground into powder.
