Dynamic range is 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.
Pentax K-S2 dynamic range
JPEG analysis: Interestingly, the Olympus scores highest here, particularly at higher ISOs. The Pentax K-S2, Canon 700D and Nikon D5500 deliver almost identical results.
Raw analysis: The pattern changes with raw files, where the E-M5 II still leads but with a smaller margin. The EOS 700D is now second best, while the Nikon D5500 and Pentax K-S2 trade places at different ISOs.