Blackmagic PYXIS 12K has a
98.8MP Full frame (35.6 x 23.3 mm ) sized CMOS sensor . On the other hand, Canon 5D MIII has a
22.0MP Full frame (36 x 24 mm ) sized CMOS sensor and features Digic 5+ processor.
Blackmagic PYXIS 12K's sensor provides 76.8MP more than Canon 5D MIII'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 PYXIS 12K and 5D MIII sensor size comparison.
Sensor Size and Resolution Comparison image of Blackmagic PYXIS 12K and Canon 5D MIII Cameras
Blackmagic PYXIS 12K and Canon 5D MIII 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
Blackmagic PYXIS 12K
or the
Canon 5D MIII ,
including hyperfocal distance.