Canon EOS 5D Mark III Instruction Manual (en)

The camera can use a CF card and SD card. Images can be recorded 
when at least one card is installed in the camera.
If a card is inserted in both slots, you can select which card to record 
images to or record the same images simultaneously on both cards 
(p.118, 120).
If you use an SD card, be sure the card’s write-protect switch 
is set upward to enable writing/erasing.
Open the cover.
Slide the cover as shown by the 
arrow to open it.
Insert the card.
The camera-front side slot is for a CF 
card, and the camera-back side slot 
is for an SD card.
Face the CF card’s label side 
toward you and insert the end with 
the small holes into the camera. 
If the card is inserted in the wrong 
way, it may damage the camera.
The CF card eject button will stick 
With the SD card’s label facing 
you, push in the card until it clicks 
in place.
Installing and Removing the Card
Installing the Card
Write-protect switch
SD card
CF card