Interrupted write
The battery died, or the card was pulled while the buffer was still emptying. The allocation table is left half-updated — the images are complete, the record describing them is not.
Very common
Unlike a failing hard drive, nothing is getting worse while it sits in a bag. The only thing that destroys what is on a corrupted card is writing — and the camera writes every time you take a frame.
Cameras, phones and Windows all respond to a corrupt card by offering to repair it, and repair means format. That one tap turns a straightforward structural recovery into a carve, and sometimes into nothing.
One instruction, and it matters more than everything below it.
A corrupted card is not deteriorating on its own. Unlike a failing hard drive, nothing is getting worse while it sits in a bag. The only thing that destroys what is on it is writing — and the camera writes every time you take a frame.
So take the card out. Not later, not after a few more shots to see whether it sorts itself out. The images you take next are written into the space the missing ones occupy, and on a burst that is dozens of files in seconds.
And decline every offer the camera makes. Cameras routinely propose to repair or format a card on power-up, and photographers accept out of habit — both write.
Cards fail in a small number of predictable ways, and most of them leave the photographs intact.
The battery died, or the card was pulled while the buffer was still emptying. The allocation table is left half-updated — the images are complete, the record describing them is not.
In-camera formats are always quick formats, because the card must be usable in seconds. Every image is physically still there behind a fresh empty index.
Cheap card readers and built-in laptop slots corrupt cards on eject more often than the cards themselves fail. Try a different reader before concluding anything.
A card claiming far more than it holds. Works perfectly until real usage passes the true size, then loses everything past that point permanently.
It explains why a card corrupts from an interruption that a computer drive would shrug off.
Cards above 32GB use exFAT, and it is deliberately lightweight: fast, broadly compatible across cameras, phones and computers, and with far less redundancy than NTFS or ext4. There is no journal recording what was about to happen, and only limited duplication of critical structures.
That design is right for removable media, where speed and compatibility matter more than resilience. It also means exFAT tolerates interruption poorly. A drive with a journal can replay or roll back an incomplete operation on the next mount; exFAT simply ends up with an allocation table that no longer matches reality, and once it does, files vanish from listings or return unreadable while their contents sit untouched in the flash.
All free, and between them they resolve a fair proportion.
Reader faults are commoner than card faults, and this separates them in two minutes. Use a decent standalone reader rather than a laptop slot if you can.
At 512GB or 1TB, a counterfeit is a genuine possibility. Free tools write across the full claimed capacity and read it back — hours on a big card, and worth it, because nothing recovers data that was never stored.
On a mechanically sound card with an intact controller, carving photographs by signature is well within what free tools manage. Recover to a different drive, never back to the card.
Undetected means the controller rather than the file system, and because cards are monolithic that means reading through test points on a sealed package. Software cannot reach it and repeated attempts achieve nothing.
Usually not. The commonest cause is an interrupted write leaving the allocation table half-updated — the images are complete and the record describing them is not. Take the card out and stop shooting.
Yes, if nothing has been shot since. Cameras use quick formats because the card must be usable again in seconds, so the images remain physically present behind a fresh empty index. The frames taken afterwards are what cost you.
No. Cameras routinely offer to repair or format on power-up and both write to the card. Decline, remove the card, and do nothing else with it until you have decided how to proceed.
Because exFAT, the format cards above 32GB use, is deliberately lightweight for speed and compatibility. There is no journal and limited duplication of critical structures, so an interrupted write leaves inconsistencies a more robust file system would recover from automatically.
Write data across the full claimed capacity and read it back, comparing what returns. A genuine card returns it all; a fake returns the earlier portion correctly and rubbish beyond its real size. Worth doing on any suspiciously cheap high-capacity card.
From £250 plus VAT for cards and USB media, fixed after a free 48-hour diagnostic, with most jobs no fix, no fee. If the diagnostic finds a counterfeit, we tell you rather than charge you to find out.