What causes RAW file corruption that shows a normal preview, then a damaged image?
Asked 7/27/2011
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2 answers
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A small number of my Canon RAW files appear corrupted after a trip. In Lightroom or Windows Explorer, the image looks normal for a moment, then part of it is replaced by a bright damaged area. In Canon Digital Photo Professional, the thumbnail looks fine, but the file will not open and is reported as corrupt.
What typically causes this kind of RAW corruption? Could it be related to heat, or is it more likely the memory card, card reader, cable, or file transfer process? Is there anything worth trying to recover the files?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
15y ago
2 Answers
4
This is often down to transfer from card to computer, not corruption on the actual card.
I have found that Windows Explorer tends to be the culprit - do not copy files from your card simply by dragging/dropping in Explorer - use a different tool.
I have used the free 'FastCopy' file copier with 100% success. It has a verification option that you can use to confirm the files copied correctly.
ps. Don't rely on the CR2 preview in explorer (if you have this shell extension enabled) because it uses the embedded preview which may be fine. To test all files in a folder, I run the Adobe DNG converter to convert to DNG files, then use the DNG shell extension (google it) to preview in explorer. This shows up corrupt DNG files (from corrupt CR2 files) easily. Then you can go back and recopy those individual files from your flash card. But I've not had this problem at all since switching to FastCopy.
Originally by user19632. Source · Licensed CC BY-SA 4.0
user19632
13y ago
0
Generated from our catalog & community — verify before relying on it.
The brief “good” image is usually the embedded JPEG preview inside the RAW file. After that, the software tries to render the actual RAW data, and if that data is damaged you see the corruption.
Based on the answers, the most likely causes are:
- a bad or failing memory card / flash memory
- a problem with the card reader or cable
- corruption during copy from card to computer
Heat is possible in theory, but the community answers consider card or transfer issues much more likely.
What to do:
- Re-copy the files from the card using a reliable copy utility with verification rather than simple drag-and-drop.
- Test with another memory card and shoot a few hundred frames to see if the issue repeats.
- Try a different card reader and cable.
- Format cards in-camera after confirming your backups.
Recovery may be limited. If the RAW data itself is corrupted, some files may not be recoverable, though RAW repair/recovery tools are worth a try. Also, don’t trust Explorer thumbnails alone, since they may only show the embedded preview, not the real RAW image data.
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AI15y ago
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