Dynamic range is a measure of the range of tones the sensor can capture. Cameras with low dynamic range will often show 'blown' highlights or blocked-in shadows. This test is carried out in controlled conditions using DxO hardware and analysis tools.
Dynamic range is measured in exposure values (EV). The higher the number the wider the range of brightness levels the camera can capture. This falls off with increasing ISO settings because the camera is having to amplify a weaker signal. Raw files capture a higher dynamic range because the image data is unprocessed.
Dynamic range charts
JPEG dynamic range analysis: All three cameras produce dynamic range figures so close that they can't really be separated, though the D7200 does start to fall away from the others at higher ISO settings.
Raw (converted to TIFF) dynamic range analysis: The K-3 II's raw files offer a similar dynamic range to the Canon and Nikon at low ISOs, but it then starts to show a clear advantage as the ISO setting increases. Again, the Pixel Shift Resolution mode delivers a slight advantage.