Both Nikon D5100 and Pentax K-50 have APS-C sized 16.0 MP resolution sensors so sensor size and resolution is not a differentiator between these two cameras.
Below you can see the D5100 and K-50 sensor size comparison.
Sensor Size and Resolution Comparison image of Nikon D5100 and Pentax K-50 Cameras
Nikon D5100 and Pentax K-50 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
Both Nikon D5100 and Pentax K-50 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, D5100 has scored 80, 1 points higher than K-50.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Nikon D5100
80
23.5 bits
13.6 Evs
1183 ISO
Pentax K-50
79
23.7 bits
13.0 Evs
1120 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
Nikon D5100
or the
Pentax K-50 ,
including hyperfocal distance.
