Sony A550 has a
14.0MP APS-C (23.4 x 15.6 mm ) sized CMOS sensor and features Bionz processor. On the other hand, Sony A900 has a
25.0MP Full frame (35.9 x 24 mm ) sized CMOS sensor and features Bionz processor.
Sony A900's sensor provides 11MP more than Sony A550's sensor, which gives a significant advantage in real life. You can print your images larger or crop more freely.
On the other hand, please keep in mind that Max sensor resolution is not the only determinant of resolving power. Factors such as the optical elements, low pass filter, pixel size and sensor technology also affects the final resolution of the captured image.
Below you can see the A550 and A900 sensor size comparison.
Sensor Size and Resolution Comparison image of Sony A550 and Sony A900 Cameras
As seen above, Sony A900 has a 2.4x Larger sensor area than Sony A550. 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. Sony A550 and Sony A900 sensors have been tested by DxO and the results show that A900 has a better overall score of 79, 13 points higher compared to A550's score of 66.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Sony A550
66
21.9 bits
11.8 Evs
807 ISO
Sony A900
79
23.7 bits
12.3 Evs
1431 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
Sony A550
or the
Sony A900 ,
including hyperfocal distance.
One thing to watch when comparing these two: they have different sensor sizes
(APS-C versus Full frame),
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.
