Both Pentax K-3 II and Sony A77 have APS-C sized 24.0 MP resolution sensors so sensor size and resolution is not a differentiator between these two cameras.
Another difference between these two cameras is that Pentax K-3 II's sensor lacks 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 K-3 II and A77 sensor size comparison.
Sensor Size and Resolution Comparison image of Pentax K-3 II and Sony A77 Cameras
Pentax K-3 II and Sony A77 have the same sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture.
DxOMark Sensor Scores
Both Pentax K-3 II and Sony A77 sensors have been tested by DxoMark. DxoMark 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. Of the two cameras that we are comparing, K-3 II has scored 80, 2 points higher than A77.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Pentax K-3 II
80
23.6 bits
13.6 Evs
1106 ISO
Sony A77
78
24.0 bits
13.2 Evs
801 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 K-3 II
or the
Sony A77 ,
including hyperfocal distance.
