I've pushed it to 200, 400, 800 and even 1600 with mixed results. Pushing to 200 is alright, 400 got poor highlights and shadows with decent grain and anything above that is fairly worthless. D76 did the best job for me. Let me look around and see if I have notes on it, but it can be done to 400 I believe. I feel like I did 1:1 in D76 for 18 minutes or something on that order.