5d Mark I Max CF Card Size and capability with a Mark III

ALthough you'd want to verify, there have been no reported problems with any modern cards not working on the original Canon 5D.

Except...! Make sure you have updated to the latest firmware 1.1.1! If you are using an older version, the camera will silently trash or brick your card if 8 GB or larger!

Personally, after the firmware update, I have used Transcend 133x cards upto 32 GB in the original 5D. Of course the camera cannot utilize the higher speeds of modern cards, but it will still work.

Load firmware 1.1.1 here.

Kind regards,
- Henrik

--
And if a million more agree there ain't no great society