I just faced a curious issue. Opened my Compact Flash drive using a card reader to delete some picture and got it corrupted. Now it won't open on Windows and isn't usable in the camera. I've got the option to format it, but I'm gonna try to save the other pictures.
My question is, can a card get corrupted by using Windows to delete files from it and how can I try to recover the pictures on it? That's really awkward!
File deletion essentially means removing file entry from file system (file system contains information about all location and size of all files on disc or memory card). If something goes wrong file system may become corrupted, rendering card inaccessible (all the data may be still there, but without filesystem you can't tell where one file begins and another ends. To make matter worse files are not guaranteed to occupy contiguous space on disc and may be broken into multiple parts).
Since neither Windows nor the camera can read the card, I think the most likely scenario is that the changes Windows were about to write to the card were interrupted halfway through.
Such interruptions will corrupt a file system for sure, and could happen if you just unplug the card instead of going through the Windows "safely remove hardware and eject media" option. (In the bottom right of the desktop, it pops up whenever you plug in a USB device. You may have to click the upward pointing triangle/arrow, with the "show hidden icons" mouseover text, in order to see it.)
Or it could happen if you suddenly lose power to the computer in the middle of a write.
The problem is that when you make changes to a storage device (hard disk, memory card etc.) the operating system doesn't write these changes to the device immediately. Instead the OS will wait a bit to see if there are more changes coming, so it can write out several changes in one go, which is much faster than doing the changes one keypress at a time. So the last few changes stay in the computer for a while, and aren't finalized (written to the card) before either the user or an OS timer requests it.
Corruption happens when the OS has started to write changes, but didn't get the chance to complete it. This can (will) leave the file system in an illegal state that cannot be read by anyone, aka corrupted.
If you have a corrupted card, the best chance to recover anything lies with a file recovery program. Some of these programs will work even if the file allocation table (the "table of contents" that tells the computer/camera which files are at which storage locations) is broken, although they may recover some garbage in the process, and some files may not be recoverable.
The simplest way to avoid such problems in the future may be to delete only through the camera menu. But as long as you do proper synchronization ("safely remove hardware...") there shouldn't be any problems. In theory.
My question is, can a card get corrupted by using Windows to delete files from it and how can I try to recover the pictures on it?
Yes, a card can get corrupt just by inserting it into a card reader, not only by deleting files. I had a multi-card reader and only the xD slot would corrupt the card. I could view them but once it was taken out it was no longer viewable on anything. (I assumed it was a virus because a wipe and clean install of the OS resolved the issue. Not my PC though.)
A card getting corrupt can happen for various reasons. Virus, read/write error, damaged sectors or processors... But not all is lost. You can google various card recovery programs but one for Windows I recommend is ZAR (Zero Assumption Recovery).
As suggested before, try to use the "remove safely" function but the best way to avoid this is once the images are backed up, format the card within the camera.
Even if you just want to view them elsewhere (other than the camera), back them up and format the card in the camera. If this doesn't resolve anything you may need to look into a new card, card reader or anti-virus program. Most likely just a card though.
Opening files from a card on Windows should not corrupt it, since that action is only doing a read, and not altering the contents.
You should never format, or delete images on anything other than the camera, primarily because of the various disk formats and implementation of them on computers.
Most cameras use the Windows format known as FAT32. This ensures compatibility with nearly any system, as Windows, Mac and most linux can read FAT32. However, some (older) cameras will use FAT (or FAT16), which can cause issues, and typically is less compliant on non-windows machines. Increasingly, cameras use exFAT, which supports files above 4GB in size (video mostly).
I add this information to point out that its difficult to tell what format a camera actually uses, and it is possible, on your PC, to choose the format type. Choose the wrong one, and the camera can no longer read it.
I never delete or format from the computer, and I uncheck the selection that offers to 'remove images after download'. Instead I put my card back in the camera, and select 'Format' from the camera menu, which deletes any images and also refreshes the format to ensure no issues on the next shoot.
For recovery, I have used PhotoRec (donationware) with shockingly good results.
When you are deleting files, windows does not actually delete them. It just writes to a a special place on the card (fat, file allocation table) that this file is deleted. If you remove the card during this write operation, whole card will be unusable since the FAT is corrupted. Luckily in many cases file recovery programs can scan your card and rebuild the FAT, or copy your files to another disk.
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