Canon’s new motor driven mirror mechanism debuted with the 7D Mark II. It’s a revolutionary new mechanism that promises reduced vibrations from the mirror flipping. The same system has been used in the new 5DS / SR. This short 43-second video demonstrates how the system works:
The mirror inside your DSLR is a prime candidate for vibration and the resulting softness of your image. In traditional spring driven mirrors, the flipping motion results in the mirror slamming against the top, creating vibration. This is a prime reason why lots of photographers prefer to use mirror lock-up when they need tack sharp images.
With the new system, the mirror decelerates when it reaches the top. Additionally, braking mechanisms in the system ensure that the mirror decelerates during down action as well. This cuts down vibrations and ensures a sharper image.