Rolling shutter

Rolling shutter describes the process of image capture in which a still picture (in a still camera) or each frame of a video (in a video camera) is captured not by taking a snapshot of the entire scene at a single instant in time but rather by scanning across the scene rapidly, vertically, horizontally or rotationally.

This produces predictable distortions of fast-moving objects or rapid flashes of light, referred to as rolling shutter effect.

[1][2] The advantage of this electronic rolling shutter is that the image sensor can continue to gather photons during the acquisition process, thus effectively increasing sensitivity.

CCDs (charge-coupled devices) are alternatives to CMOS sensors, which are generally more sensitive and more expensive.

Final results depend on the readout speed of the sensor and the nature of the scene being filmed; as a rule of thumb, higher-end cinema cameras will have faster readout speeds and therefore milder rolling shutter artifacts than low-end cameras.

Animation showing the rolling shutter effect
A de Havilland Canada Dash 8 Q-400 six-blade propeller, with severe rolling-shutter distortion from a Pixel 3 camera
A Eurocopter EC-120 helicopter – the rotor blades seem to be swept back more than usual due to the rolling-shutter effect.
Simulation of the rolling-shutter effect on a rotating propeller and a moving car
(click for SMIL animation)