How did you managed to get over 50 frames in such resolution? With 6d in 1280x720p i am getting 1840x632 (and yes, usually 53 frames), but when i set 1920x1080 i get 1840x1221 and not more than 29 frames. I have sandisk extreme 45 MB/s but i think, that in this moment it doesnt matter, everything probably is about buffer size...