You’ve got a photo that looks great on the camera display, but when you open it on your computer the image looks ruined, as if someone applied a glitch effect to it. Don’t panic! You might be able to save the picture.

When I photographed the ruins of an 1950s air raid siren on a tower, I returned to my computer and one of the images I liked the most appeared like this in Adobe Photoshop Lightroom:

This is not good. When you see a pattern of strangely colored rectangles over part or all of a digital photograph, sometimes with rough stripes running through them, that’s a sign that the image data is corrupted. It’s messed up and unusable. I didn’t panic, because after thinking it through I realized that there was a chance that the file corruption happened while reading the card or transferring the image to the computer. If that was true, the original image data on the card might be OK, and the photo might transfer properly if I try again. And that’s what I did. I copied the photo from the card to the computer again and got this:

At first, that looks like bad news. This one’s also corrupted. But wait a minute: It isn’t corrupted in the same way. That could mean that the corruption really isn’t in the original, because if it was, I’d expect the result to look exactly the same. This encouraged me to give it another try:

Aha! As they say, the third time’s the charm. The image was perfect. The hope I had clung to was correct: The original image was good after all, I just needed to complete a successful transfer of it. What went wrong? I’m still not sure. If it had continued to fail I might have tried my other card reader to see if it did any better. As it is, I don’t know if it was the card reader, the cable, or what. There are a few lessons to take away from this.

• Verify your images after the shoot by looking through them on a computer or other device. If they are camera raw images, look at the previews generated by your raw processor. For the images above, the JPEG preview image attached to the raw file by the camera looked fine; it wasn’t until Lightroom read through all the raw data and produced its own preview that the problem was evident.
• If it looks like you might have a corrupted image, it might be worth it to keep trying to copy it off the card until it works.
• To preserve the option to copy the image again, you must not erase or format the camera media until you verify the images on your computer. If I had formatted the camera card immediately after import and before I discovered the problem, I would not have been able to go back and try again.

The card I used is relatively new, so there is still a chance that there’s something wrong with it. My next step with the card will be to format it in the camera. Hopefully that’ll help fix whatever went wrong. If it starts happening again, I’ll have to troubleshoot using process of elimination to find out whether the problem is in the card, the card reader, or the USB cable.

Update: I’ve isolated the problem to a defective USB card reader. I switched card readers after the errors became more frequent, and the new card reader produces no problems reading the same cards while connected to the same USB cable.