What is the purpose of a .ctg file and the MSCANON directory - and can I delete them?
The mysterious .ctg file
You've probably plugged your canon memory card into your computer and noticed a .ctg file sitting in a directory called 'CANONMSC'. Typically the CTG is called something like M0100.CTG (it can vary - see below for more details). Being the curious type, you are probably wondering what they do and can you delete them?
The short answer is simple. Leave the .ctg file and CANONMSC directory as they are. CTG stands for catalog (or 'catalogue' for our UK English visitors) and its pupose is to allow you to view contents of different folders and the card without having to manually change between folders. This is particularly important if your camera is set to create new folders every day, week or month, or if you take more than 10000 photos and the default counter ticks over from IMG_9999 back to IMG_0001. The same files are used by software provided with the camera (eg ZoomBrowser EX and ImageBrowser) to import and rename files from the memory card. Typically the files are tiny - a CTG is less than 1KB (but it may take up to 32KB because of that is the minimun size a file can occupy on a card). So it's not worth worrying about.
As a general rule, if you accidentally delete the file, the camera will regenerate the CTG files next time you load the card into your camera and turn it on. The name of the CTG file is linked to the folder containing the photos. The first three digits of the folder dictate the last three of the CTG file name. 100CANON will have a CTG file M0100.CTG, 101CANON will have a CTG file M0101.CTG.
As mentioned above, the CTG files are tiny and perform only a cataloging function. They do not contain any photos. Even with these files missing, you can still manually copy files from your memory card to your computer using Windows Explorer. However, if your photos are missing and you are attempting file recovery, the CTG file will not assist in recovering the photos (so you can ignore them).
The .ctg file located in the CANONMSC directory.
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