Data Recovery Case File · Cameras, Drones & Cards · The Worst Possible Overlap

New Footage Fills a Card From the Front, Which Is Where the Missing Clips Were

His enquiry describes a loss with an unlucky geometry. Footage copied off after a shoot where "the first hour or so of clips had not copied over — I have since wiped the card in camera and also shot a fair few clips on it before realising." The missing material is the earliest, and new recording begins at the front of a wiped card, so the footage that failed to copy is sitting exactly where the replacement footage went.

The decode: why the overlap is so unfavourable, and what may survive

What the wipe did on its own: cleared the index and marked the capacity available. The clips were not erased by it — at that moment, everything including the untransferred hour was still physically present.

Why that is worth stating: had he noticed before shooting again, this would have been a straightforward recovery of the whole missing portion. The wipe was survivable, and the subsequent recording was not.

Why the geometry is the cruel part: cameras fill a card sequentially from the beginning. The first clips of the original shoot occupied the front of the card, and the first clips of the new session occupied the front too — so the replacement footage landed directly on the material that had not been copied.

Why the clips that did copy were the lucky ones: they sat further into the card. The transfer captured everything after a point, and what it missed was the earliest portion — which is also the portion most exposed to being written over first.

How much survives, and what determines it: how much was recorded after the wipe. If the new session used less of the card than the missing hour occupied, the tail of that hour may lie beyond the new footage and still be present.

Why that makes the quantity of new recording the key question: a few clips leaves most of the missing hour untouched beyond them; a full session leaves very little. He describes a fair few clips, which suggests partial rather than complete overlap — worth establishing precisely.

What can be recovered from a partial overlap: whatever lies beyond the reach of the new recording. That is likely to be the later part of the missing hour rather than its beginning, which is the reverse of the order he would probably prefer.

Why video carves comparatively well within that: clips are large and written in long continuous runs. A clip that begins beyond the overwritten region is recoverable in full rather than in fragments, so results tend to be whole clips or nothing rather than damaged ones.

Why the card must come out of use now: anything further recorded extends the overwritten region further into the card. Each additional session reduces what remains of the missing hour, and it is the only variable still under his control.

What the process lesson is, and it is the general one: the transfer was not verified against the source. A copy that silently omits a portion is only detectable by comparison, and the card was cleared on the assumption that the copy was complete rather than on a check that it was.

On the bench

The sequential fill pattern was assessed to establish overlap between lost and replacement footage — cameras filling a card from the beginning, so the earliest clips of a shoot occupy the region that a subsequent session's first clips also occupy, placing untransferred early material directly beneath new recording. A wipe alone clears the index while leaving clips present, so the subsequent recording rather than the wipe determines loss. Carving was targeted across unallocated and unreached regions.

The outcome

The fill pattern assessed to establish overlap, the card withdrawn from use, and carving targeted to unreached regions. Free assessment, one fixed written figure including VAT; on cards where content has been overwritten, the figure is payable upfront. The decode: the wipe was survivable and the shooting afterwards was not. Cameras fill from the front, so your missing first hour is exactly where the new clips went — and what survives is whatever the new session did not reach.

Our case files are drawn from genuine enquiries received by our laboratory over the past ten years, anonymised to protect client confidentiality. Each one describes the diagnostic and recovery procedure our engineers apply to that fault, using the equipment listed.