Both Fujifilm X20 and Fujifilm X100 have 12.0 MP resolution sensors but Fujifilm X20's sensor is 2/3-inch (8.8 x 6.6 mm ) and Fujifilm X100's sensor is APS-C (23.6 x 15.8 mm ).
Since Fujifilm X100'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 X20.
One other difference between these two cameras that is worth mentioning is that Fujifilm X100'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 X20 and X100 sensor size comparison.
Sensor Size and Resolution Comparison image of Fujifilm X20 and Fujifilm X100 Cameras
As seen above, Fujifilm X100 has a 6.4x Larger sensor area than Fujifilm X20. 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
Fujifilm X20
or the
Fujifilm X100 ,
including hyperfocal distance.
One thing to watch when comparing these two: they have different sensor sizes
(2/3-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.
