Canon EOS 5D - Manual (Page 70)

70
The file number is like the frame number on a roll of film. It can start
counting in one of three different ways: [Continuous], [Auto reset], and
[Manual reset]. The images you take are automatically assigned a file
number from 0001 to 9999. The images are saved in the selected
folder.
1
Select [File numbering].
Turn the <5> dial to select [c File
numbering], then press <0>.
2
Select the file numbering method.
Turn the <5> dial to select
[Continuous], [Auto reset], or
[Manual reset], then press <0>.
The file numbering continues in sequence even after you replace the
CF card. This prevents images from having the same file number, so
image management with a personal computer is easier. Note that if the
replacement CF card already contains images captured with the
camera, the file numbering will start after the highest file number in that
CF card or after the last captured image’s file number, whichever is
higher.
3 File Numbering Methods
Continuous
XXX-0051
CF card -1
XXX-0052
CF card -2
File numbering after
changing the CF card
Next sequential file number