Some interesting specs of the Canon EOS-1D X compared to the Nikon D4:
- Sensor: 18.1 MP sensor, 17.9 MP effective (D4: 16.6 and 16.2 MP respectively)
- Framerate: 12/14 fps (D4: 10/11 fps)
- Buffer: 35 raw files (D4: 69 – 98 raw files, depending on bit depth and compression)
Note: with the ultra fast XQD cards, Nikon's effective buffer capacity is probably even higher.
- ISO: 50–204800 (D4: Same)
Note: I have not yet seen a comparisons of their respective low light performance, so it remains to be seen whether or not Nikon still remains the low light champion, like in the last couple of years.
- AF: 61 points (D4: 51)
Note: D4's AF works in one stop lower light and with up to f/8 lenses, Canon only goes to f/5.6 lenses.
- Exposure Bracketing: up to ±3 (D4: up to ±5)
- Video: 1920x1080@30/25/24fps, 1280x720@60/50fps, 640x480@30/25fps (D4: 1920x1080@30p/25p/24p, 1280x720@60p/50p/ 30p/25p, 640x424@30p/25p, So very similar if not the same)
Note: While Nikon has uncompressed video out capabilities, Canon does not.
28 Feb 2012 update: new buffer size info for the Canon added (previously unknown).