Canon EOS R3 Advanced User's Manual page 786

Directory structure of the target folder
Configured in [FTP server] → [Directory structure].
With [Default], the root folder is used for image storage. If you have created a subfolder in
the root folder by changing the [Target folder] setting, images are saved in that folder.
Selecting [Camera] automatically creates a folder structure matching that of the camera's
(such as A/DCIM/100EOSR3) in the server's root folder for image storage. If you have
created a subfolder in the root folder by changing the [Target folder] setting, a folder
structure such as A/DCIM/100EOSR3 is automatically created in that folder for image
storage.
Overwriting files of the same name
Configured in [FTP server] → [Overwrite same file].
With [Overwrite same file] set to [Disable]
If there is already a file with the same name in the target folder on the FTP server, the new
file is saved with an extension consisting of an underscore and a number, as in
IMG_0003_1.JPG.
When you resend images if initial transfer fails
Even if the camera is configured to overwrite files of the same name, if you resend an image
file that could not be transferred initially, the existing file may not be overwritten in some
cases. If this happens, the new file is saved with an extension consisting of an underscore, a
letter, and a numeral, as in IMG_0003_a1.JPG.
Passive mode
Configured in [FTP server] → [Passive mode].
Enable this setting in network environments protected by a firewall. If an Error 41 occurs
(Cannot connect to FTP server), setting passive mode to [Enable] may enable access to the
FTP server.
Trusting target servers
Configured in [FTP server] → [Trust target server].
Set to [Enable] if you prefer to connect to FTP servers even when trust cannot be
established based on the root certificate used. In this case, take suitable security measures.
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