Both Leica SOFORT 2 and Sigma SD15 have 5.0 MP resolution sensors but Leica SOFORT 2's sensor is 1/5-inch (2.56 x 1.92 mm ) and Sigma SD15's sensor is APS-C (20.7 x 13.8 mm ).
Since Sigma SD15'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 Leica SOFORT 2.
One other difference between these two cameras that is worth mentioning is that Sigma SD15'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 SOFORT 2 and SD15 sensor size comparison.
Sensor Size and Resolution Comparison image of Leica SOFORT 2 and Sigma SD15 Cameras
As seen above, Sigma SD15 has a 58.3x Larger sensor area than Leica SOFORT 2. 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
Leica SOFORT 2
or the
Sigma SD15 ,
including hyperfocal distance.
One thing to watch when comparing these two: they have different sensor sizes
(1/5-inch 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.
