Pentax K20D has a
15.0MP APS-C (23.4 x 15.6 mm ) sized CMOS sensor . On the other hand, Olympus E-M5 has a
16.0MP Four Thirds (17.3 x 13 mm ) sized CMOS sensor and features TruePic VI processor.
Below you can see the K20D and E-M5 sensor size comparison.
Sensor Size and Resolution Comparison image of Pentax K20D and Olympus E-M5 Cameras
As seen above, Pentax K20D has a 1.6x Larger sensor area than Olympus E-M5. 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. Pentax K20D and Olympus E-M5 sensors have been tested by DxO and the results show that E-M5 has a better overall score of 71, 6 points higher compared to K20D's score of 65.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Pentax K20D
65
22.9 bits
11.1 Evs
639 ISO
Olympus E-M5
71
22.8 bits
12.3 Evs
826 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 K20D
or the
Olympus E-M5 ,
including hyperfocal distance.
One thing to watch when comparing these two: they have different sensor sizes
(APS-C versus Four Thirds),
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.
