I'm having a hell of a hard time finding ISO 12800 content, and I shoot my 50 normally, and it doesnt get that high of ISO. I have ISO 1600 sample ETTR'd 2 stops, but that doesnt prove much. I dont think I have any 12800 and ettr'd that much.
I'd be happy with say ISO1600 no EC, ISO3200 w/+1 and ISO6400 w/+2 
















