Both Pentax K-m and Canon 400D have APS-C sized 10.0 MP resolution sensors so sensor size and resolution is not a differentiator between these two cameras.
Below you can see the K-m and 400D sensor size comparison.
Sensor Size and Resolution Comparison image of Pentax K-m and Canon 400D Cameras
As seen above, Pentax K-m has a 1.1x Larger sensor area than Canon 400D. 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
Both Pentax K-m and Canon 400D sensors have been tested by DxoMark. DxoMark 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. Of the two cameras that we are comparing, K-m has scored 64, 2 points higher than 400D.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Pentax K-m
64
22.4 bits
11.4 Evs
513 ISO
Canon 400D
62
22.1 bits
11.0 Evs
664 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
Pentax K-m
or the
Canon 400D ,
including hyperfocal distance.
