1Dx HDR image
Unlike the 5D mk3, the 1Dx doesn't have a built in ability to produce HDR images but, since it has such a high frame rate, it can produce hand held HDR images quite well.
Here is one at ISO 25,600 with 3 images 1.7 stops apart, RAW, processed in LR, no noise reduction and merged in Photoshop:
|High Altitude Rocky Mountain Railroad by cjf2|
from On the Rails...
|Evening at the lake. by Murat ÜNSAL|