Sony A6300 has a
24.0MP APS-C (23.5 x 15.6 mm ) sized CMOS sensor and features BIONZ X processor. On the other hand, Sigma BF has a
24.6MP Full frame (36 x 24 mm ) sized CMOS sensor .
One other difference between these two cameras that is worth mentioning is that Sigma BF's sensor doesn't have an 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 A6300 and BF sensor size comparison.
Sensor Size and Resolution Comparison image of Sony A6300 and Sigma BF Cameras
As seen above, Sigma BF has a 2.3x Larger sensor area than Sony A6300. 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 A6300
or the
Sigma BF ,
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.