Both Canon 7D and Canon 1D X have 18.0 MP resolution sensors but Canon 7D's sensor is APS-C (22.3 x 14.9 mm ) and Canon 1D X's sensor is Full frame (36 x 24 mm ).
Since Canon 1D X's has a larger sensor area with the same resolution, this means that it also has a larger pixel area hence better light collecting capacity for a given aperture compared to Canon 7D.
Below you can see the 7D and 1D X sensor size comparison.
Sensor Size and Resolution Comparison image of Canon 7D and Canon 1D X Cameras
As seen above, Canon 1D X has a 2.6x Larger sensor area than Canon 7D. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in same focal length and aperture.
DxOMark Sensor Scores
DxOMark is a benchmark that scientifically assesses image quality of camera sensors. It scores camera sensors for color depth (DXO Portrait), dynamic range (DXO Landscape) and low-light sensitivity (DXO Sports), and also gives them an overall score. Canon 7D and Canon 1D X sensors have been tested by DxO and the results show that 1D X has a better overall score of 82, 16 points higher compared to 7D's score of 66.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Canon 7D
66
22.0 bits
11.7 Evs
854 ISO
Canon 1D X
82
23.8 bits
11.8 Evs
2786 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 7D
or the
Canon 1D X ,
including hyperfocal distance.
One thing to watch when comparing these two: they have different sensor sizes
(APS-C versus Full frame),
so compare them at the same framing rather than the same focal length.
Put the same focal length on the smaller sensor and it will show less depth of
field, not more, because it also crops tighter. The calculator shows the
full frame equivalent focal length for each body so you can match the framing.
