Cards fail in a small number of predictable ways, and in most of them the images are intact behind a broken index or a struggling controller. What you do in the first few minutes decides whether that stays true.
Every device that reads a corrupt card offers to fix it, and fixing means formatting. That single click converts a routine recovery into a carving job — and sometimes into nothing.
Cards use FAT32 or exFAT, and the file allocation structures are updated constantly during shooting. Pull the card mid-write, let the battery die during a burst, or eject without unmounting, and those structures are left inconsistent. The device then reports the card as corrupt, unformatted or unreadable — while every photograph remains exactly where it was written.
That is the good case and it is the common one. Recovery means rebuilding the index, or carving the images out by their signatures if the index is beyond repair, which works because JPEG and RAW files have distinctive headers.
Cards also fail physically. The controller can die, at which point the card is not detected at all or reads a fraction of its real capacity. Wear is genuine on cards used heavily for video, where the same blocks are rewritten constantly.
The other cause worth naming is counterfeit media. A card advertised as 512 GB but built on 32 GB of flash with altered firmware will appear to accept everything and then corrupt catastrophically once real usage passes the actual capacity. If a card was unusually cheap and failed suddenly with large amounts of data on it, this is a likely explanation — and recovery is limited to whatever genuinely landed on real flash.
First, take the card out and try a different reader — built-in laptop slots are frequently the fault, and a decent USB reader costs little. Second, try another computer. Third, if the card mounts at all, copy everything off immediately before attempting any repair, even if the folder structure looks wrong.
What not to do: don’t run chkdsk, which writes to the card and discards entries it cannot reconcile; don’t let the camera fix it; and don’t keep shooting on it, because new images will land on the space holding the old ones.
Memory cards are from £250 +VAT after a free 48-hour diagnostic and a written quote, and most jobs are no fix, no fee. Send the card on its own in a rigid case rather than in the camera. If you know roughly how many images are missing and when they were taken, mention it — it helps confirm the right material has come back rather than simply a large amount of it.
Usually, yes. Most card corruption is damage to the FAT or exFAT index rather than to the images, so the photographs are still physically present. They can be recovered by rebuilding the index or carving them out by signature, since JPEG and RAW files have distinctive headers.
No — that is the single action most likely to cost you the photos. Formatting rewrites the index that recovery would use. Decline the prompt from Windows, macOS and especially the camera, which offers it the moment you power on with the card inserted.
Usually because the file allocation structures were left inconsistent — the card was removed mid-write, the battery died during a burst, or it was ejected without unmounting. The images themselves are generally untouched.
Try a different reader first, since built-in laptop slots fail often, then another computer. If it is still undetected, the controller has probably failed — which is a physical recovery rather than something software can address, but frequently still recoverable.
Memory cards and USB sticks are from £250 plus VAT, fixed in a written quote after a free 48-hour diagnostic. Most jobs are no fix, no fee. Send the card on its own rather than inside the camera.