I shoot a lot of HDR with 5-7 frames per shot. When I turned on SD backup in slot 2, the storage process took a hit. I have to wait for the buffer to clear between frame sets. I push the cable release button down half way and read the rX number in the viewfinder to see how many image spaces are available in my buffer before I pull the trigger. When the number exceeds my intended number of HDR frames, I shoot.