Sigma fp L has a
61.0MP Full frame (36 x 24 mm ) sized BSI-CMOS sensor . On the other hand, Nikon Z5 has a
24.0MP Full frame (35.9 x 23.9 mm ) sized CMOS sensor and features Expeed 6 processor.
Sigma fp L's sensor provides 37MP more than Nikon Z5'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.
Below you can see the fp L and Z5 sensor size comparison.
Sensor Size and Resolution Comparison image of Sigma fp L and Nikon Z5 Cameras
Sigma fp L and Nikon Z5 have almost the same sensor size, so neither of them has any significant advantage over the other in terms of providing control over depth of field when used with the 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
Sigma fp L
or the
Nikon Z5 ,
including hyperfocal distance.