Leica M Instruction Manual page 235

Notes:
• Simple formatting does not cause the data on the card to be
irretrievably lost. Only the directory is deleted, which means that
the existing files are no longer directly accessible. The data can be
accessed again using appropriate software. Only the data that is
then overwritten by saving new data is actually permanently
deleted. You should nevertheless get into the habit of transferring
all your pictures onto a secure bulk storage medium, e.g. the hard
drive on your computer, as soon as possible. This is particularly
important if the camera is being sent for servicing along with the
memory card.
• Depending on the memory card used, formatting can take up to 3
minutes.
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