The Lumix GH4 camera I shoot is one of the only cameras on the market (so far) that captures 4K video. Suffice it to say, that 4K is the highest resolution currently obtainable. In fact the resolution is so high, that the camera can export individual frames from a video sequence, and each can stand on their own as still images. Some (lazy ;-) photographers are saying they can now shoot an entire event in 4K and just pull the stills from the footage! As an artist first... that doesn't work for me. I'm being paid for my skill and "vision" using camera settings, composition and lighting to create unique images.
HOWEVER, it is a very useful feature. These shots were captured when I had the couple ride towards me on their Harley's. Not easy to make adjustments, follow focus, etc. while they are coming at you... but a snap to shoot 4K video and extract the stills later. Check it out: