Just installed the Canon C100 firmware upgrade that Canon released last November. I made a trip up to White Horse Hill during the storm last night. I set the camera to 320 iso then racked through all the levels till 80,000. (I couldn't see what I was filming unless I looked at the LCD screen on the camera.) Didn't use any noise reduction in camera or in post. Some shots had a 20 watt outside lamp giving some light and the last shot is lit by my car head lights on dipped. The noise is awful. But any light that is around the camera will put to good use. I used an old nikkor 50mm F1.4 Ais lens. Enjoy.
(few typos in the 2am version)