Canon Wireless File Transmitter WFT-E2 II A Instruction Manual page 60

Choosing Recording Media When Shooting
[Record/play] Setting
When you select external media in [Record/play], the [Select location for DCIM folder]
screen is displayed. The DCIM folder contains the EOS1D folder, where images are stored.
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To create the DCIM folder in the first folder
displayed when the external media is opened (that
is, the root directory), select the default setting of [/].
To create another parent folder for the DCIM
folder, select [Create folder]. A screen is
displayed for entering the folder name.
By default, the folder name comprises the current
date (last two digits of the year, in addition to the
month and day) and numbers representing the
order the folder was created, in a range of 01 to
99.
Always use 8 characters for the folder name.
For instructions on entering the folder name, refer to
"Virtual Keyboard Operation" (p.20).