Both Nikon D7500 and Nikon D6 have 21.0 MP resolution sensors but Nikon D7500's sensor is APS-C (23.5 x 15.7 mm ) and Nikon D6's sensor is Full frame (35.9 x 23.9 mm ).
Since Nikon D6'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 Nikon D7500.
Another difference between these two cameras is that Nikon D7500's sensor lacks 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 D7500 and D6 sensor size comparison.
Sensor Size and Resolution Comparison image of Nikon D7500 and Nikon D6 Cameras
As seen above, Nikon D6 has a 2.3x Larger sensor area than Nikon D7500. 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.
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 D7500
or the
Nikon D6 ,
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.
