Sigma DP2 Quattro has a
20.0MP APS-C (23.5 x 15.7 mm ) sized CMOS (Foveon X3) sensor and features TRUE III engine processor. On the other hand, Canon G1 X III has a
24.0MP APS-C (22.3 x 14.9 mm ) sized CMOS sensor and features DIGIC 7 processor.
Below you can see the DP2 Quattro and G1 X III sensor size comparison.
Sensor Size and Resolution Comparison image of Sigma DP2 Quattro and Canon G1 X III Cameras
As seen above, Sigma DP2 Quattro has a 1.1x Larger sensor area than Canon G1 X III. 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.
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
Sigma DP2 Quattro
or the
Canon G1 X III ,
including hyperfocal distance.