Sony A58 has a
20.0MP APS-C (23.2 x 15.4 m ) sized CMOS sensor . On the other hand, Pentax K-3 has a
24.0MP APS-C (23.5 x 15.6 mm ) sized CMOS sensor and features Prime III processor.
One other difference between these two cameras that is worth mentioning is that Pentax K-3's sensor doesn't have an anti-alias (Low-Pass) filter. Removing anti-alias filter increases the sharpness and level of detail but at the same time, it increases the chance of moiré occurring in certain scenes.
Below you can see the A58 and K-3 sensor size comparison.
Sensor Size and Resolution Comparison image of Sony A58 and Pentax K-3 Cameras
Sony A58 and Pentax K-3 have almost the same sensor size, so neither of them has any significant advantage over the other in terms of providing control over depth of field when used with the 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 A58 and Pentax K-3 sensors have been tested by DxO and the results show that K-3 has a better overall score of 80, 6 points higher compared to A58's score of 74.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Sony A58
74
23.3 bits
12.5 Evs
753 ISO
Pentax K-3
80
23.7 bits
13.4 Evs
1216 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 A58
or the
Pentax K-3 ,
including hyperfocal distance.
