That's a compressed H.265 image made from a ProRes4444 source file. The resulting file size is approximately 1% of the source file size yet shows almost no compression artifacts.
We are following the developments of the H.265 codec very closely, because it's likely to be a real game-changer in terms of quality level. If you haven't been following this codec, it's worth taking a look at. We have a long way to go before it's widely adopted, since there will need to be dedicated encoder and decoder chips on cameras and playback systems to encourage more people to use it. But with Netflix and other streaming services on board for 4k streaming in this format, it probably won't take long to get there. Our prediction is that NAB 2014 will be all about this codec.
The folks over at <a href="http://www.eoshd.com/content/11534/new-h-265-codec-test-prores-4444-quality-1-file-size">EOSHD.com</a> have a pretty good overview of the format, including links to comparison images of the frame above with the ProRes 4444 original.