Canon uses an industry standardised EXIF file naming scheme. The file naming part is designed as follows
filename structure
[four characters][four digits].Extension
so IMG_1234.JPG or IMG_1234.CR3 are valid filename.
EXIF standard also defines that images captured with sRGB and AdobeRGB color spaces should be differentiated. When the camera is set to AdobeRGB the initial character will be set to underscore. So filename become
_MG_1234.JPG and _MG_1234.CR3
Additionally the standard defines the folder structure used on the card. Images are stored in the DCIM folder then subfolders are created with the following structure.
[three digits][five characters]
For example 100CANON or 100EOSR5
Since only four numeric digits are used for the filename there can only be a maximum of 9999 images in a folder. When image IMG_9999 has been written the camera creates a new folder 101CANON and starts numbering the files from 0001 again.
Filenames and folders use uppercase characters only.
Brian
EOS specialist trainer, photographer and author
-- Note: my spell checker is set for EN-GB, not EN-US --
