Ricoh GR IV HDF has a
26.0MP APS-C (23.5 x 15.6 mm ) sized CMOS sensor . On the other hand, Leica X-U has a
16.0MP APS-C (23.6 x 15.7 mm ) sized CMOS sensor .
Ricoh GR IV HDF's sensor provides 10MP more than Leica X-U'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.
Another difference between these two cameras is that Ricoh GR IV HDF's sensor lacks 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 GR IV HDF and X-U sensor size comparison.
Sensor Size and Resolution Comparison image of Ricoh GR IV HDF and Leica X-U Cameras
Ricoh GR IV HDF and Leica X-U 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
Ricoh GR IV HDF
or the
Leica X-U ,
including hyperfocal distance.