Corrupted digital images recoverable?
August 13, 2005 7:56 PM   Subscribe

Girlfriend just got back from a trip abroad and looks like many of her SD cards are acting funny. Are corrupted images and *.CHK files recoverable? (more inside)

Looks like windows detected problems with one or two of them and ran scandisk on them because it has created those recovered files directories with a bunch of filenames with the extension of .CHK Most of them are about 16kb but some looked large enough to me images, so i renamed a few to .jpg and opened and sure enough some OLD OLD OLD pictures showed just fine even though they were one or two years old, ones that her mom swears she deleted a long time ago.
First question is, what are these files and are they related to this next problem?

A few images are now showing up only halfwayish, with the rest of the image being all grey in photoshop, with some other image apps saying they are corrupted. Is there any way to fix these?

FURTHERmore.... She claims she's missing quite a few images that aren't showing up anywhere. Could these be scattered about in the .CHK files? And still recoverable?

Her mom apparently hasn't been "ejecting" the cards correctly in windows, which could be one reason why the filesystems are being screwy. But the cards themselves feel very flimsy. Could it be a combination of wear on the cards, brokeass filesystems, and aliens?

I'm used to CF cards and never had a problem with them so this stumped me...
posted by joshgray to Computers & Internet (2 answers total)
If the boot sector of a disk gets corrupted, Scandisk will do truly hideous things to the file system in the process of attempting to fix it - mostly because it likes to write scandisk.log out to the corrupted file system. I don't think you need to invoke wear on the cards or aliens - a brokeass file system is quite capable of producing the behaviour you've seen.

This article from Linux Journal has a pretty good rundown on how a knowledgeable person can use the tools available on just about any modern Linux distro to fix stuff like you've got. Find a friendly geek and bribe with pizza and beer.
posted by flabdablet at 8:45 AM on August 14, 2005

First question is, what are these files and are they related to this next problem?

The way a filesystem works, nothing is normally deleted. Overwritten, yes, but not deleted. There's a master index that tells the computer what files are where. When a file is "deleted", it's simply telling the index, "You can write over this."

So, let's say you fill up a card full of pictures. Then you deleted all the pictures. They're still there, you just can't see them (you can recover them, however). Let's say you half-fill up the card with NEW pictures. Those old pictures will be overwritten. If you run a recovery program on the card, you'll only be able to recover half of the old pictures (the half that wasn't overwritten).

Is there any way to fix these?

Kinda-sorta. The .CHK files aren't necessarily complete files. When Windows doesn't know how big a file is supposed to be (which might happen if a boot record were corrupted, for example), it will use the default sector size. On Win32 formatted drives, that's something like 16k. Unfortunately, while the data could be correct, it's could be scattered over several .CHK files. You could use a HEX editor, load up a bunch of files in order, and search for the JPEG header for the start of each file, but it would probably be a lot easier to just use a Flashcard Recovery Program like SanDisk's RescuePro or File Scavenger.
posted by Civil_Disobedient at 1:34 PM on August 14, 2005

« Older TrialByJuryFilter   |   Is it worth $2500 to learn Transcendental... Newer »
This thread is closed to new comments.