How does the compression work on Canons . Can you choose a bitrate in the menu? Is it decided by the SD slot speed? Decided by the card speed as well? Is it always a consistent speed in All-I? And if so does anyone know the max bitrate for the 6D? (I think it's. 90 for Mark IIi) Just curious cuz I don't wanna but an SD card with a super high write speed if it isn't even capable.