Canon 1D X III has a
20.0MP Full frame (36 x 24 mm ) sized CMOS sensor and features Digic X processor. On the other hand, Canon R5 II has a
45.0MP Full frame (36 x 24 mm ) sized Stacked CMOS sensor and features Digic X processor.
Canon R5 II's sensor provides 25MP more than Canon 1D X 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.
Below you can see the 1D X MIII and R5 Mark II sensor size comparison.
Sensor Size and Resolution Comparison image of Canon 1D X III and Canon R5 II Cameras
Canon 1D X III and Canon R5 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 Canon 1D X III has 124% larger pixel area compared to Canon R5 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
Canon 1D X III
or the
Canon R5 II ,
including hyperfocal distance.
