Both Sony A99 and Canon SL2 have 24.0 MP resolution sensors but Sony A99's sensor is Full frame (35.8 x 23.8 mm ) and Canon SL2's sensor is APS-C (22.3 x 14.9 mm ).
Since Sony A99'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 SL2.
Below you can see the A99 and SL2 sensor size comparison.
Sensor Size and Resolution Comparison image of Sony A99 and Canon SL2 Cameras
As seen above, Sony A99 has a 2.6x Larger sensor area than Canon SL2. 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 Sony A99 and Canon SL2 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, A99 has scored 89, 10 points higher than SL2.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Sony A99
89
25.0 bits
14.0 Evs
1555 ISO
Canon SL2
79
23.6 bits
13.4 Evs
1041 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
Sony A99
or the
Canon SL2 ,
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.