How to offload camera cards safely

1. Two copies, on two different drives

   One drive fails, gets dropped or stolen. Copy every card to at least two physically separate drives, ideally kept in different places by the end of the day.

2. Verify with checksums, not file sizes

   A copy can have the right size and still be corrupt. Compare a checksum of every file (xxHash64 is fast and standard on set) between the card and each copy.

3. Read the copy back from disk

   Right after copying, the system may still hold the data in memory. A check that reads from memory proves nothing about the drive. Verify by reading back from disk.

4. Keep the proof with the media

   Write ASC MHL and a report next to the files on every drive, so post, the lab or an archive can verify the backup again years later.

5. Format only after every drive is verified

   Safe to eject is not safe to format. The card goes back into the camera only when every file on every drive matches.

6. Name and log every card

   Use one folder per shooting day and per card, keep the card name the camera gave it, and keep a day report so the production knows what was shot and where it is.

mmMover reads the card once, writes all drives at the same time, verifies every file from disk, and writes ASC MHL and a report on each drive. How it works · ASC MHL explained · FAQ