Both Sony A99 and Fujifilm X-A3 have 24.0 MP resolution sensors but Sony A99's sensor is Full frame (35.8 x 23.8 mm ) and Fujifilm X-A3's sensor is APS-C (23.5 x 15.7 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 Fujifilm X-A3.
Below you can see the A99 and X-A3 sensor size comparison.
Sensor Size and Resolution Comparison image of Sony A99 and Fujifilm X-A3 Cameras
As seen above, Sony A99 has a 2.3x Larger sensor area than Fujifilm X-A3. 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
Sony A99
or the
Fujifilm X-A3 ,
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.
