Nikon D3X has a
25.0MP Full frame (35.9 x 24 mm ) sized CMOS sensor and features Expeed processor. On the other hand, Sony A99 II has a
42.0MP Full frame (35.9 x 24 mm ) sized BSI-CMOS sensor and features Bionz X processor.
Sony A99 II's sensor provides 17MP more than Nikon D3X's sensor, which gives a significant advantage in real life. You can print your images larger or crop more freely.
On the other hand, please keep in mind that Max sensor resolution is not the only determinant of resolving power. Factors such as the optical elements, low pass filter, pixel size and sensor technology also affects the final resolution of the captured image.
One other difference between these two cameras that is worth mentioning is that Sony A99 II'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 D3X and A99 II sensor size comparison.
Sensor Size and Resolution Comparison image of Nikon D3X and Sony A99 II Cameras
Nikon D3X and Sony A99 II 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. On the other hand, since Nikon D3X has 72% larger pixel area compared to Sony A99 II, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.
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 D3X and Sony A99 II sensors have been tested by DxO and the results show that A99 II has a better overall score of 92, 4 points higher compared to D3X's score of 88.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Nikon D3X
88
24.7 bits
13.7 Evs
1992 ISO
Sony A99 II
92
25.4 bits
13.4 Evs
2317 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 D3X
or the
Sony A99 II ,
including hyperfocal distance.
