Canon 1D X II has a
20.0MP Full frame (36 x 24 mm ) sized CMOS sensor and features Dual DIGIC 6+ processor. On the other hand, Nikon D3X has a
25.0MP Full frame (35.9 x 24 mm ) sized CMOS sensor and features Expeed processor.
Nikon D3X's sensor provides 5MP more than Canon 1D X II's sensor, which gives a significant advantage in real life. You can print your images larger or crop more freely.
On the other hand, please keep in mind that Max sensor resolution is not the only determinant of resolving power. Factors such as the optical elements, low pass filter, pixel size and sensor technology also affects the final resolution of the captured image.
Below you can see the 1D X MII and D3X sensor size comparison.
Sensor Size and Resolution Comparison image of Canon 1D X II and Nikon D3X Cameras
Canon 1D X II and Nikon D3X have almost the same sensor size, so neither of them has any significant advantage over the other in terms of providing control over depth of field when used with the same focal length and aperture.
DxOMark Sensor Scores
At Camera Decision, we also look at Dxo Mark sensors when available as we think it is a good indicator of image quality.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Canon 1D X II
88
24.1 bits
13.5 Evs
3207 ISO
Nikon D3X
88
24.7 bits
13.7 Evs
1992 ISO
Sensor size sets the circle of confusion, so it drives how much depth of field each
of these bodies gives you at a given aperture. You can calculate it exactly for the
Canon 1D X II
or the
Nikon D3X ,
including hyperfocal distance.