Sony A7S III has a
12.0MP Full frame (35.6 x 23.8 mm ) sized BSI-CMOS sensor and features Bionz XR processor. On the other hand, Panasonic S1 II has a
24.0MP Full frame (35.6 x 23.8 mm ) sized Partially-Stacked CMOS sensor and features Venus Engine processor.
Panasonic S1 II's sensor provides 12MP more than Sony A7S III's sensor, which gives a significant advantage in real life. You can print your images larger or crop more freely.
On the other hand, please keep in mind that Max sensor resolution is not the only determinant of resolving power. Factors such as the optical elements, low pass filter, pixel size and sensor technology also affects the final resolution of the captured image.
One other difference between these two cameras that is worth mentioning is that Panasonic S1 II'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 A7S III and S1 II sensor size comparison.
Sensor Size and Resolution Comparison image of Sony A7S III and Panasonic S1 II Cameras
Sony A7S III and Panasonic S1 II have the same sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture. On the other hand, since Sony A7S III has 99% larger pixel area compared to Panasonic S1 II, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.
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 A7S III
or the
Panasonic S1 II ,
including hyperfocal distance.
