Olympus E-P1 has a
12.0MP Four Thirds (17.3 x 13 mm ) sized CMOS sensor and features TruePic V processor. On the other hand, Sony A55 has a
16.0MP APS-C (23.5 x 15.6 mm ) sized CMOS sensor and features Bionz processor.
Below you can see the E-P1 and A55 sensor size comparison.
Sensor Size and Resolution Comparison image of Olympus E-P1 and Sony A55 Cameras
As seen above, Sony A55 has a 1.6x Larger sensor area than Olympus E-P1. 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. Olympus E-P1 and Sony A55 sensors have been tested by DxO and the results show that A55 has a better overall score of 73, 18 points higher compared to E-P1's score of 55.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Olympus E-P1
55
21.4 bits
10.4 Evs
536 ISO
Sony A55
73
23.0 bits
12.4 Evs
816 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
Olympus E-P1
or the
Sony A55 ,
including hyperfocal distance.
One thing to watch when comparing these two: they have different sensor sizes
(Four Thirds 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.
