Rolling vs Global Shutter - What's the difference??

In the past, film cameras utilized a physical mask or shutter to prevent light from exposing the film until the shutter was released. Nowadays, digital SLR cameras also use a physical shutter to control light entry into the sensor and optimize light exposure. In addition to the camera body shutter, the sensor electronics integrate a digital shutter that regulates how the sensor reads the image data to form the final image. This is done using either a Rolling Shutter or a Global Shutter method.

Rolling vs Global Shutter - What's the difference?

Rolling Shutter:

A rolling shutter captures images by scanning the camera's pixel array line-by-line. This means the image is captured one row at a time, from top to bottom. As a result, if there is any movement in the scene, it can cause distortion in the image. This is because each line is captured at a slightly different time, leading to a warped or skewed image.

Global Shutter:

On the other hand, a global shutter captures the entire image at once. This means there is no distortion caused by movement in the scene, as the whole image is captured simultaneously. Global shutter sensors use a mechanism to synchronize the exposure of all sensor pixels, ensuring that the image is captured accurately.?

Which one is better?

While both types of shutters have pros and cons, the global shutter is generally considered superior for most applications. This is because it can capture more accurate and less distorted images, especially when there is movement in the scene. However, rolling shutter can be a more cost-effective option for certain applications, as it is simpler to implement. To understand this better, I highly recommend watching SmarterEveryDay's Video on Rolling Shutter

As you can see above, rolling shutter distortion differs from motion blur. Occurs when an object or camera is in motion, fast enough that it causes compression or expansion of the object in the captured image due to the timing of the read-out of pixel rows. It can create funky still frames of objects in motion!?

If the spinning coin above was captured with a global shutter, it would appear normal, frozen in time. So why use global shutter for regular applications? In scientific and engineering applications such as live cell imaging, imaging flow cytometry, robotic vision systems, or industrial inspection, it may be important to achieve non-distorted images using a global shutter. Furthermore, any application with external lighting that is flashed or strobed will see tremendous benefits from utilizing a global shutter camera with the flash pulse synchronized to the camera. This Fstoppers video explains the benefits global shutter cameras will have in SLR flash photography very well.?

Wrapping it up

In conclusion, the choice between rolling and global shutters largely depends on the specific application and the desired outcome. While rolling shutter may be a more cost-effective option, it can cause distortion in the final image, especially when there is movement in the scene. On the other hand, a global shutter can capture more accurate and less distorted images, making it a preferred choice for most applications. Nevertheless, it is always advisable to assess the needs of the specific application to determine which shutter type will be most suitable.