Rolling shutter is a common issue with many cameras that you have likely encountered at some point, but there is another technology that circumvents all those issues: the global shutter. This great video discusses what a global shutter is and why it is such a desirable thing.
Coming to you from ProAV TV, this excellent video discusses global shutters and why they are a desirable technology. The majority of modern CMOS sensors employ rolling shutters, which refers to the way the sensor scans the image. With a rolling shutter, the image is scanned sequentially line by line (normally from top to bottom). The problem with this is that all data is not recorded simultaneously, meaning that if there is significant motion across the frame during this time, artifacts can be introduced. On the other hand, a global shutter records all image data simultaneously, eliminating the issues of a rolling shutter. Nonetheless, a global shutter is not universally better. Rolling shutter designs tend to have less noise and better dynamic range while also producing less heat than comparable global shutters, and they are also much cheaper, thus why we see them in most cameras. Check out the video above for more!
Also, for the photo people, that means you get to sync your flash at any speed.
I was hoping to learn how fast the rolling shutter reads. If a modern processor operates at Gigaherz clock speed, then the time difference between the top & bottom line will be milli or micro seconds. IE, insignificant unless you're doing high speed photography.
If you try to quick pan on a Hybrid DSLR camera, you get a distorted frame in which all vertical lines are leaning. Also, I remember the Godox iPhone trigger flash has a top sync speed of 1/30, that should be your answer to the "how fast" question.
Fun fact: in the film days, you could get "rolling shutter" with any camera with a focal-plane shutter, too!
That is, as long as the shutter speed was faster than the flash sync speed, because the two curtains then exposed a moving "stripe" of film, rather than the entire image.
At the "flash sync speed," one shutter fully opened before the other shutter began closing, and thus, the ultra-fast flash burst could expose the entire frame.