Watching your own hand movements through your phone camera is a good demonstration of this. Set 60 Hz video mode, and the latency is probably less than 30 ms - but still extremely obvious.

it's quite a lot more than 30ms, as phone cameras do some real heavy-weight image processing to compensate for their tiny size, I'm talking neural networks and such. the throughput might be 60fps when it's all conveyor-ed but the latency sure isn't