Both Nikon P7100 and Canon 40D have 10.0 MP resolution sensors but Nikon P7100's sensor is 1/1.7-inch (7.44 x 5.58 mm ) and Canon 40D's sensor is APS-C (22.2 x 14.8 mm ).
Since Canon 40D'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 Nikon P7100.
Below you can see the P7100 and 40D sensor size comparison.
Sensor Size and Resolution Comparison image of Nikon P7100 and Canon 40D Cameras
As seen above, Canon 40D has a 7.9x Larger sensor area than Nikon P7100. 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. Nikon P7100 and Canon 40D sensors have been tested by DxO and the results show that 40D has a better overall score of 64, 23 points higher compared to P7100's score of 41.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Nikon P7100
41
19.4 bits
10.7 Evs
165 ISO
Canon 40D
64
22.1 bits
11.3 Evs
703 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
Nikon P7100
or the
Canon 40D ,
including hyperfocal distance.
One thing to watch when comparing these two: they have different sensor sizes
(1/1.7-inch versus APS-C),
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.
