Rolling shutter artifacts are distortions or visual anomalies that can occur in images or videos captured by cameras with rolling shutter sensors. A rolling shutter is a type of image sensor that captures an image by scanning or exposing different parts of the frame sequentially rather than all at once. The exposure starts at one edge of the frame and moves to the other, typically from top to bottom or vice versa.
The rolling shutter process can lead to several artifacts:
Skew or wobble: Because not all parts of the image are exposed simultaneously, fast-moving objects or rapid camera motion can cause skew or wobbling effects. For instance, vertical lines may appear slanted if the camera or the objects in the scene are moving horizontally.
Motion distortion: Rapidly moving objects or panning the camera quickly can result in distortion, making objects appear stretched or skewed.
Jello effect: When the camera experiences vibrations or shakes, the rolling shutter can produce a jello-like effect, causing vertical lines to warp or bend.
Temporal aliasing: Objects in motion may exhibit strange patterns or distortions, especially when their movement frequency aligns with the rolling shutter scan rate. This can create visual artifacts known as temporal aliasing.
Flash banding: When using a flash in combination with a rolling shutter, bands of uneven illumination may appear in the image due to the asynchronous timing between the flash and the rolling shutter.
These artifacts are more pronounced in cameras with slower rolling shutters or when capturing fast-paced action. Global shutter sensors, which expose the entire image at once, do not suffer from rolling shutter artifacts but are often more expensive and less common in consumer-grade cameras. Filmmakers and photographers need to be aware of rolling shutter artifacts when using cameras with this type of sensor and take precautions to minimize their impact, such as using slower camera movements and avoiding rapid panning.