Here's a quick test I did because I had both the Sony X200 and PMW-400K - notice how close the sensitivity is at the various gain levels:
https://youtu.be/3qNA2gU97fs

Some of the help the X200 gets is from it's image processing. Granted, the 400K uses 2/3'' sensors, it may need less processing to get to it's sensitivity level.

Faster lenses might help in the 400K's situation, whereas the X200 is a fixed lens camera. I have no doubts a X300 is coming soon. I hope they remove the software lockout of higher voltages on the DC IN that they introduced on the PMW-300.

In the world of 2/3" B4 lenses, ENG/EFP's are pretty much stuck at f1.8. A long time ago, the first gen IF Canon wide J8x6 went to f1.6. :)

Paul

I'm talking about using SLR lens adapters with a 50mm 1.4 or something similar.

I like ENG lenses, but expanding using a 2x extender to Super35 isn't efficient. I like 2/3'' to MFT cause x2 is exactly 4/3''. Really wishing the AF200 would come out.