# What's caused this image corruption?



## toutou (May 13, 2015)

Hi,

I'm experiencing some problems with a few images that appear to be corrupt - the files open in Lightroom 4 and are initially fine, but some of them go weird after a while (not sure what to call it but see the image).

I have never experienced this problem before so I'm wondering what the problem might be. 

Here are some points


All of the problematic images appear to come from the same SD card. It doesn't affect all images on the card though.
Once the image has gone weird in Lightroom, it also appears corrupted in Finder. If I re-import the image from the SD card, it's fine at first. Then it might go corrupt again BUT if I play with the levels in Lightroom, the corruption goes and the image is fine.
Everything is fine on the camera and there was no indication that some images might be corrupted.

The images were taken on a 600D in raw format, with Magic Lantern installed (stable version) and on SanDisk Extreme card (32GB, 45MB/s). Never experienced any issues before with any of these. 

The only thing I have done differently to other times when I've added images to Lightroom is that I have put the images on an external HD because there isn't enough space on my Macbook. Again, never had problems with the HD and it seems to be working just fine (it's USB2).

What could the problem be?

Thanks


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## neuroanatomist (May 13, 2015)

I'd suspect the card.


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## AcutancePhotography (May 13, 2015)

Is it possible for you to give the card to someone else who has LR and see if the problem can be repeated? Part of the diagnostic process is trying to replicate the problem while reducing the variables.


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## suburbia (May 13, 2015)

have had this before. Lightroom builds the preview image that is viewed when using Lightroom modules as a separate JPEG on import so it seems to suggest the import from the card was successful.

My conclusion would therefore be a corruption during the transfer to the external USB drive, are you using a USB2 hub rather than directly connecting it to the USB2 port on the laptop? If not the next guess would be a flaky USB2 interface on the external drive or even a dodgy cable. Then next guess would be a dodgy power supply to the external Hard Drive, any power outage at time?

I got such a corruption when transferring my RAW files to some new hard drives set up on a new but cheap RAID PCI card. The corruptions were only apparent when rebuilding the Lightroom preview files or when exporting.


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## zim (May 13, 2015)

_The only thing I have done differently to other times when I've added images to Lightroom is that I have put the images on an external HD because there isn't enough space on my Macbook_

As Acutance says, reduce the variables. I'd take just that one picture copy it to your MacBook (I assume it's got enough space for that!) (actually could that be the issue that LR is running out of cache space?) anyway does the corruption still happen on that pic, if so it's not your external drive.

Regards


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## dlee13 (May 13, 2015)

Do you delete images in camera? That can cause a corruption of some of the files. It's happened to me before as well.


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## toutou (May 13, 2015)

This makes me think it might have been the transfer from the card to the HD because one of the transfers took 5-6 hours - I'm not sure if it was the card in question or the other one I used (also 32GB) but it was quite strange. 

The card reader is also USB2 but everything goes directly into the computer. The HD is powered through USB, so no external power. Perhaps that's a problem as well (it's a newish, small Western Digital though and I would have thought it should be handle a 20-32GB transfer... but perhaps the cable moved in the process, who knows).

What I don't get is why the image goes corrupt again once I've re-imported it from the card (with the same process). Does Lightroom have a cache of some sort and once I change some of the levels, it updates the cache and hence restores the image?

I will try importing the images in question to the computer directly to see what happens. I've opened them on my work computer with the same card reader and there don't appear to be any problems.

And yes I have deleted images in camera - it's a bit alarming that that can cause issues because surely people do that all the time!

Thanks everyone


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## suburbia (May 13, 2015)

so you still have the original RAW file on the CF card? I would just view it directly on the card itself via the USB2 card reader with a MAC OS RAW viewer or use the Canon EOS utility. That will prove where the corruption occurred.

Lightroom creates a preview file from the RAW file either during the import process if you have always create preview files selected or during the develop module process. These files exist in a cache which can be cleared, clear Preview File cache option.

Might be worth clearing your Preview File cache and deleting the previous import from the catalog and then re-importing from the card if viewing the RAW files directly on the card show no corruption.


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## mnclayshooter (May 13, 2015)

I've seen this nearly exact same distortion/corruption when I had a faulty SD card. I've never (knock on wood) seen it in my DSLR, but I have seen it on my Phone when shooting directly to an off-brand name card. Since switching to a reputable card mfr, I've never seen the issue. The funny thing about it.... when I review the image on the phone, the image comes up fine... when I transfer it elsewhere, it is corrupted, which leads me to believe that it is an embedded "thumbnail" image that I'm seeing on the phone vs what is seen when I open the native file on the PC. 

To be fair... the microSD card in question was an off-brand name/store-branded card... when I replaced it with a SanDisk card, I had a similar issue that the card wouldn't stay mounted to the OS in the phone, but SanDisk had a known issue on that specific serial number/size card. Since switching to another SanDisk card, I've never seen the problem. 

Not an apples-to-apples comparison, for certain, however, the corruption was nearly identical.


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