Ricoh CX1 has a
9.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CMOS sensor and features Smooth Imaging Engine IV processor. On the other hand, Canon SD4000 IS has a
10.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized BSI-CMOS sensor and features Digic 4 processor.
Below you can see the CX1 and SD4000 IS sensor size comparison.
Sensor Size and Resolution Comparison image of Ricoh CX1 and Canon SD4000 IS Cameras
Ricoh CX1 and Canon SD4000 IS have the same sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture. On the other hand, since Ricoh CX1 has 11% larger pixel area compared to Canon SD4000 IS, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.
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
Ricoh CX1
or the
Canon SD4000 IS ,
including hyperfocal distance.