Increased Sensitivity due to CFA Removal:
I’ve determined more accurately that the EV difference before and after the conversion of this Sony sensor is +1 EV. I used RawDigger as my measuring tool to measure the values on either side of the half converted sensor. The lighting was evenly placed on a gray card, and exposed to just below clipping—exposed to the right (ETTR). The small square in the image below near center is the area of measurement for the color side, and it was moved just to the other side of center (monochrome) for the second measurement. This sensor is currently open to the environment with no other filters between the lens and sensor.
This increase in EV is due to just the removal of the CFA, and not of the CC or AA filter—the effect of those two filters would be equal across the entire sensor. Leaving those filters off does, however, increase sensitivity by allowing more light to fall upon the sensor. Even more sensitivity can be expected from shooting outdoors. I’ve noticed a +1.5 to 2 EV increase when shooting in daylight with a full spectrum converted camera.
Go HERE to see an image of a converted sensor magnified to 200x.