Leica M Instruction Manual page 96

Note:
As long as this function is active, all other camera functions are
blocked.
Important:
Use only the USB cable supplied with the hand grip.
While data is being transferred from the camera to the computer,
the connection may not under any circumstances be broken by
removing the USB cable, as otherwise the computer and/or the
camera may crash, and the memory card may even be irreparably
damaged.
While data is being transferred from the camera to the computer,
the camera must not be turned off or turn itself off due to a lack of
battery capacity, as otherwise the computer can crash. If the
capacity battery capacity runs low while transferring data, end the
data transfer, turn off the camera (see p. 150) and charge the
battery (see p. 141).
DATA STRUCTURE ON THE MEMORY CARD
When the data stored on a card is transferred to a computer, the
following folder structure is used:
Up to 9999 pictures can be stored in each of the folders 100LEICA,
101LEICA etc.
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