NatureScapes.net Forums

Sorting through a backlog of photos and I came across two (exactly 100 shots apart) that are corrupt. Taken with 50D which at the time was running the first shipped firmware version. I'm just curios about what might have caused this, and maybe I can prevent it in future. Camera gave no error at the time that I recall. I would have downloaded to Hyperdrives in the field then from there to PC. The thumbnails looked ok so I subsequently reformatted the cards and Hyperdrives. These probably would have been trash anyway so if this was an isolated thing I'm not too worried.
Converted at default settings in ACR, resized and saved for web.

and at 100%:

That is usually what happens when you have a corrupted File Allocation Table and that is usually caused by a power interruption while writing the card or possibly a defective card. Basically the file can be written do different parts of a card in a non-contiguous way (called file fragmentation). If the pointer for where the different file fragments are is wrong, missing or otherwise damaged, you will get results like this.

In the past this would occur if you popped the CD card door open prior to the camera finishing writing to the card. Newer cameras usually will interrupt the writing but resume it if you close the door. But if you don't or pop the card out before it's done, you can get a result like this. Another way this can happen is if you pull a battery while the card is still being written to.

Yet another way this can happen is if you put the card in a card reader attached to your PC and just pull the card rather than properly ejecting it. I can probably come up with a dozen other reasons but somewhere in the chain, if the card is not defective, the card lost power while a write operation was going on.

It's also possible the files were fine on the CF card, but were corrupted during or after being copied onto the PC. Transfers from card readers can corrupt files without errors, though this is rare. File pointers can be corrupted or lost on the computer's file system, though most computers are now using file system structures that are more robust than the FAT16 / FAT32 type of structure used on camera flash memory. If the files were corrupted on the card, there's nothing you can do besides try to avoid situations like E.J. describes. If they were corrupted during the copy onto the PC, you can check for this and re-copy at the time, prior to wiping the cards. If they became corrupted on the PC at a later date, then you need backups that you can recover.

At any point you are checking images, you might consider doing so using an application that actually renders the raw image data, rather than just showing the JPEG previews embedded within the RAW files. The above images might still have JPEG previews that look fine, leading to a false sense of security that the images are okay when in fact the data has been corrupted.

Or you can do low-level comparisons between source and destination image copies using a utility like CDCheck to ensure that copies are valid. This won't do anything useful if the source is already corrupted, but at least it can ensure that copies haven't introduced any problems.

Thanks guys. I am fairly sure it wasn't a power interrupt that I caused. I might utilise the Hyperdrive's verification ability more but it does slow transfers down. I hope it isn't another case of connection failures of some sort in the body.
Cheers,
Neil.

Be sure to format your card quickly. FAT tables are quirky to begin with. Formatting is a good measure to protect yourself from File Allocation issues. And of course, if it seems to happen with one card much more than with others, well, you know it is probably the card's fault.

I had this problem a few years ago and could never figure out what caused it.
However sometimes when using a different RAW converter the images would open fine.
After a new PC,I never encountered this.

I had similar problems when I used a few cheap CF cards. Even since I switched to use SanDisk cards, I have never seen these again.

These would have been on Sandisk E3.