Sony A1 II has a
50.0MP Full frame (35.9 x 24 mm ) sized Stacked CMOS sensor and features Dual Bionz XR processor. On the other hand, Sony A7R IV has a
61.0MP Full frame (35.8 x 23.8 mm ) sized BSI-CMOS sensor and features Bionz X processor.
Sony A7R IV's sensor provides 11MP more than Sony A1 II'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 Sony A7R IV'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 A1 Mark II and A7R IV sensor size comparison.
Sensor Size and Resolution Comparison image of Sony A1 II and Sony A7R IV Cameras
Sony A1 II and Sony A7R IV 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
Sony A1 II
or the
Sony A7R IV ,
including hyperfocal distance.
