Nikon D300 has a
12.0MP APS-C (23.6 x 15.8 mm ) sized CMOS sensor and features Expeed processor. On the other hand, Pentax K-5 IIs has a
16.0MP APS-C (23.7 x 15.7 mm ) sized CMOS sensor and features Prime II processor.
One other difference between these two cameras that is worth mentioning is that Pentax K-5 IIs'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 D300 and K-5 IIs sensor size comparison.
Sensor Size and Resolution Comparison image of Nikon D300 and Pentax K-5 IIs Cameras
Nikon D300 and Pentax K-5 IIs 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. Nikon D300 and Pentax K-5 IIs sensors have been tested by DxO and the results show that K-5 IIs has a better overall score of 82, 15 points higher compared to D300's score of 67.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Nikon D300
67
22.1 bits
12.0 Evs
679 ISO
Pentax K-5 IIs
82
23.9 bits
14.1 Evs
1208 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 D300
or the
Pentax K-5 IIs ,
including hyperfocal distance.
