The increased focus on low-light performance seems to have paid off: The Canon EOS-1D X’s DxOMark Sports Score (based on low-light ISO), was among the best of all Canon DSLR sensors tested so far and close to that of the best-scoring sensor, the Nikon D3s, which scored a 3253 ISO compared to the 1D X’s 2786 ISO. In fact, a difference in low-light ISO of 25 percent represents 1/3 EV and is only slightly noticeable, so the difference between the Nikon D3s and the 1D X is even less so.
As Canon’s flagship professional DSLR, the 1D X’s DxOMark Overall Score of 82 is the highest of Canon’s full-frame sensors, scoring equivalently to both the new midrange Canon 5D Mark III (which received an 81) and Canon’s previous image quality winner, the 1Ds Mark III (which received an 80), but trails full-frame DSLRs from Nikon, such as the Nikon D800E and D800, which scored significantly higher at 96 and 95 respectively, as did the Nikon D4 (89), which is the 1D X’s closest competitor.
Relatively poor performance on the DxOMark Landscape Score (based on dynamic range) no doubt accounts for the weaker overall score. The 1D X’s score of 11.8 Evs is well below the highest scoring DSLRs with a good 53 cameras scoring higher, including the Nikon D4.