On-Set DIT Workflows

A Digital Imaging Technician (DIT) on a film set has one job that matters above all others: never lose a frame. Camera cards are reformatted and reused. The original files must be copied correctly to multiple destinations before that happens. There is no undo.

The problem

Traditional DIT tools compute checksums after copying, creating an MD5 or XXH file as a verification record. This works, but:

• Verification happens after the fact — you copy, then check
• The checksum file is a flat list with no directory structure
• You can’t diff two checksum files to see what changed
• The format is tool-specific and not composable

The C4 approach

C4 integrates identification with copying. The c4m file is created during the copy, not after.

Copy from card to three destinations

Using c4sh’s cp command, which wraps copying with C4 identification:

eval "$(c4sh shell-init)"
cp /mnt/card_A/ /mnt/shuttle_drive/ /mnt/onset_raid/ /mnt/dit_workstation/

You can also create a manifest of the card first, then use it for verification:

c4 id /mnt/card_A/ > day12_cardA.c4m

After copying to each destination, diff the manifest against the copy to confirm integrity:

c4 diff day12_cardA.c4m /mnt/shuttle_drive/day12/cardA/

Empty output means the copy is perfect. If any file has a mismatch, you know immediately — before the card is reformatted.

Verify later

Days later, before the shuttle drive goes to the lab:

$ c4 diff day12_cardA.c4m /mnt/shuttle_drive/day12/cardA/

Empty output confirms the shuttle drive still matches the original card contents exactly.

Diff across days

At the end of the week, see everything that was shot:

$ c4 diff monday.c4m friday.c4m

Or find exactly which new footage appeared each day — useful for dailies, lab orders, and editorial handoff.

Chain of custody

The c4m file is a cryptographic receipt. It proves:

• What was on the card — every file, every byte, identified
• When it was captured — timestamps from the filesystem
• That copies are identical — same C4 IDs across all destinations

Keep the c4m files. They’re small — a few KB even for thousands of files. They’re your proof that the camera originals were handled correctly from card to archive.

Working with existing tools

The c4m format is plain text. It can be imported into existing production tracking systems, attached to camera reports, or archived alongside the footage. No proprietary format, no vendor lock-in.

# How many frames on today's cards?
grep '.ari' day12_*.c4m | wc -l

# Find a specific clip across all days
grep 'A001_C003' day*.c4m

Standard Unix tools work on c4m files because they’re just text.