A mechanical shutter is used to expose a camera’s entire film sensor to light simultaneously, avoiding the problems produced by rolling shutters.
In film work, the only type of shutter is a mechanical shutter, but in digital sensors, images are often scanned one horizontal line at a time, reducing processing overhead but introducing rolling shutter artifacts.
There has been a move in modern digital camera design toward the implementation of mechanical shutters in digital cameras to eliminate the post-production problems caused by mechanical shutters.