what is rolling shutter

Image Acquisition Methods and Artifacts

Sequential Image Capture

Describes a methodology where different parts of a scene are recorded at different times, rather than all at once. This contrasts with global methods.

Mechanism in Electronic Sensors

Explains how certain types of image sensors, particularly CMOS sensors, capture frames by scanning across the sensor array, typically from top to bottom. This sequential readout results in lines of the image being exposed and recorded at slightly different instances in time.

Distortion Artifacts

Details the visual anomalies that arise from sequential image capture, particularly when the camera or the subject being recorded is in motion. Common manifestations include:

  • Skew: Vertical objects appear to lean or slant, especially during horizontal camera movement.
  • Wobble (Jello Effect): Unstable or vibrating appearance, most noticeable with rapid camera shaking or vibrations.
  • Partial Exposure: The top and bottom of the image may represent different moments in time, potentially capturing only parts of fast-moving objects.

Causes and Contributing Factors

Discusses factors that exacerbate distortion, including:

  • Sensor Readout Speed: Slower readout speeds increase the time differential between the capture of different parts of the frame, making artifacts more pronounced.
  • Object Velocity: Faster movement of the subject relative to the camera increases the distortion.
  • Camera Movement: Rapid panning, tilting, or vibrations contribute significantly to visible artifacts.

Mitigation Strategies

Presents techniques to reduce or eliminate these artifacts, such as:

  • Faster Sensor Readout: Employing sensors with higher readout speeds minimizes the time difference across the frame.
  • Image Stabilization: Optical or electronic image stabilization can reduce the impact of camera shake.
  • Software Correction: Post-processing algorithms can compensate for some of the distortion effects.
  • Global Capture Methods: Using cameras employing global capture methods where the entire image is captured simultaneously.