Both Sony a5100 and Nikon D600 have 24.0 MP resolution sensors but Sony a5100's sensor is APS-C (23.5 x 15.6 mm ) and Nikon D600's sensor is Full frame (35.9 x 24 mm ).
Since Nikon D600's has a larger sensor area with the same resolution, this means that it also has a larger pixel area hence better light collecting capacity for a given aperture compared to Sony a5100.
Below you can see the a5100 and D600 sensor size comparison.
Sensor Size and Resolution Comparison image of Sony a5100 and Nikon D600 Cameras
As seen above, Nikon D600 has a 2.4x Larger sensor area than Sony a5100. 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 a5100 and Nikon D600 sensors have been tested by DxO and the results show that D600 has a better overall score of 94, 14 points higher compared to a5100's score of 80.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Sony a5100
80
23.8 bits
12.7 Evs
1347 ISO
Nikon D600
94
25.1 bits
14.2 Evs
2980 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 a5100
or the
Nikon D600 ,
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.
