Both Casio EX-Z270 and Pentax K200D have 10.0 MP resolution sensors but Casio EX-Z270's sensor is 1/2.5-inch (5.744 x 4.308 mm ) and Pentax K200D's sensor is APS-C (23.5 x 15.7 mm ).
Since Pentax K200D'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 Casio EX-Z270.
Below you can see the EX-Z270 and K200D sensor size comparison.
Sensor Size and Resolution Comparison image of Casio EX-Z270 and Pentax K200D Cameras
As seen above, Pentax K200D has a 14.9x Larger sensor area than Casio EX-Z270. 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
Casio EX-Z270
or the
Pentax K200D ,
including hyperfocal distance.
One thing to watch when comparing these two: they have different sensor sizes
(1/2.5-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.
