Nikon D810A has a
36.0MP Full frame (35.9 x 24 mm ) sized CMOS sensor and features EXPEED 4 processor. On the other hand, Nikon D3X has a
25.0MP Full frame (35.9 x 24 mm ) sized CMOS sensor and features Expeed processor.
Nikon D810A's sensor provides 11MP 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.
Below you can see the D810A and D3X sensor size comparison.
Sensor Size and Resolution Comparison image of Nikon D810A and Nikon D3X Cameras
Nikon D810A and Nikon D3X 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 48% larger pixel area (35.33µm 2 vs 23.83µm 2 ) compared to Nikon D810A, it has larger pixel area to collect light hence potential to have less noise in low light / High ISO images.
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 D810A
or the
Nikon D3X ,
including hyperfocal distance.
