Rolling Shutter Exposure:
The sensor activates exposure row by row, progressing sequentially from the top to the bottom of the image, similar to a rolling curtain descending. Each row of pixels has a slightly different start and end time for exposure, resulting in a minor time discrepancy. Most CMOS sensors adopt this mode, utilizing row-by-row scanning circuitry to control the timing of light sensing for each row, enabling continuous image capture.

Global Shutter Exposure:
All pixels start and end exposure simultaneously, treating the entire exposure process "equally." Some CCD sensors, for example, use a global shutter structure to ensure all pixels capture light at the same time before reading the signals uniformly. This guarantees consistent exposure timing across all areas of the image.

Rolling Shutter vs. Global Shutter: Key Differences

Rolling shutter and global shutter are two distinct exposure modes for image sensors, differing primarily in exposure timing and imaging effects.

Rolling Shutter:
Operates like a "rolling curtain," scanning and exposing rows sequentially from top to bottom. Since each row is exposed at a slightly different time, CMOS sensors commonly use this method. However, when capturing fast-moving objects, the time lag between rows can cause the "jello effect"—distortion or skewing in the image. Despite this, rolling shutter sensors are simpler in design, more cost-effective, and suitable for everyday static photography or general surveillance.

Global Shutter:
Exposes all pixels simultaneously, freezing motion instantly. Often used in CCD sensors, this mode eliminates motion distortion, making it ideal for high-speed scenarios like sports photography or industrial inspection. However, global shutter sensors require more complex circuitry for synchronized control, leading to higher costs. Additionally, exposure time adjustments are hardware-limited. Thus, they are primarily used in specialized fields demanding high dynamic precision, such as autonomous driving and scientific imaging.

Summary:
Rolling shutter is cost-efficient but prone to motion artifacts, while global shutter delivers distortion-free imaging at a higher cost—each catering to different application needs.