I know that this is an old discussion topic...but I just am trying to clarify things for my (old) brain.
Regarding how the 5DIII records to to the two different card types, my readings and my own findings with my
camera tell me that:
1. If I write to the CF Card ONLY the write speed will be native to that card (with or without an SD card in the camera). i.e. a 600X card will record at or about 45MB/sec.
2. If I write to the SD Card ONLY the camera can only write up to 20MB/sec regardless as to the write-speed of the SD card that I put in the card slot. i.e. If I put a 600x SD card in the slot with 45MB/sec rated speed, the Camera will only be able to write to that card at 20MB/sec.
3. If I have a CF card and an SD card in each slot, both rated at 45MB/sec and set the camera to write to both cards simultaneously, in the same image type to each card (i.e. RAW, Jpeg, etc.), when I record an image, both cards will be written to at the slower, 20MB sec rate.
4. If I set the camera to write to both cards with different imaged types (i.e. write RAW to the CF and Jpeg to the SD, or visca-versa the writing will take a longer time than if the camera was set to write the same type of image to each card as in #3 above.
What is the fastest CF card that the camera can write to at the cards native write speed? i.e. how fast can the camera write to a CF card?
Any input to confirm 1-4 above or to increase my understanding of my camera would be welcome...I think I have it correct..but I could be wrong.