Previously, I created some high quality 4K video clips with Nikon V2 camera. While the buffer depth of Nikon V2 was 60 frames regardless of frame rate, it could not be used for shooting continuous 4K video.
Now, with Panasonic GH4, I can shoot 4K video directly and continuously. The workflow is clearly more convenient than shooting with Nikon V2. Quality-wise, the RAW photo based video from Nikon V2 was unbeatable. However, the compressed video format of GH4 offers a clear advantage in lower consumption of storage space.
GH4 records 4K video in the consumer grade YUV420 format. That mean, the video contains full 4K monochrome video with color information in full HD quality. It may not match those broadcast grade 4K products, but the quality is respectable. The bottomline is, you will get nearly flawless video and significant improvement over GH2/GH3 on full HD monitor.
Here is a demo clip I recorded: