Both Canon 6D and Canon 70D have 20.0 MP resolution sensors but Canon 6D's sensor is Full frame (36 x 24 mm ) and Canon 70D's sensor is APS-C (22.5 x 15 mm ).
Since Canon 6D'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 Canon 70D.
Below you can see the 6D and 70D sensor size comparison.
Sensor Size and Resolution Comparison image of Canon 6D and Canon 70D Cameras
As seen above, Canon 6D has a 2.6x Larger sensor area than Canon 70D. 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
Both Canon 6D and Canon 70D sensors have been tested by DxoMark. DxoMark 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. Of the two cameras that we are comparing, 6D has scored 82, 14 points higher than 70D.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Canon 6D
82
23.8 bits
12.1 Evs
2340 ISO
Canon 70D
68
22.5 bits
11.6 Evs
926 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
Canon 6D
or the
Canon 70D ,
including hyperfocal distance.
One thing to watch when comparing these two: they have different sensor sizes
(Full frame versus APS-C),
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.
