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I'll leave it up to you to decide if this is sufficiently on-topic. It does relate to SD cards used in photography specifically.

My Nikon D7000 does something funny to my SD cards and I can't figure out what is going on. The cards have been working fine and still work fine in the camera (photos gets recorded, no issues), but 2 of my cards have now stopped working in my PC. The computer doesn't see a card being present at all.

I've worked around the problem so far by taking an unaffected card and copying the images across using my camera (the D7000 has two SD card slots), but I'm quite uncomfortable with cards failing like this. Does anyone have similar experiences? What is causing this and how can I restore the cards?

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Please indicate how you read the cards into your computer. – Itai Apr 1 '12 at 2:18
@Itai, I use a cheap USB SD card reader, one of those you sometimes get bundled with a card. – SoftMemes Apr 2 '12 at 12:16
I have that same problem. Except with me, my cards only work in certain computers – J. Walker Apr 2 '12 at 19:23
I'd say this is definitely on topic here. However, the point of using Stack Exchange sites is to find experts on your particular topic -- and I'm not aware of any SD experts hanging out in photo.stackexchange. "Does X behavior indicate my SD card is failing, and what should I do about?" is probably more likely to find the appropriate experts on some other Stack Exchange site. – drewbenn Apr 3 '12 at 18:45
can you view the photos, new and old, in the camera? – Skaperen Jul 22 '15 at 12:22

Regarding the function of the sdcard/s in question: If a card is reading and writing without issue inside your camera, that’s a good sign that card is functioning properly. However, you can try the following:

  1. After backing up the data on the sdcard, format it with your camera.
  2. Insert the card into your reader and check if your PC 'sees the card.’
  3. If the card does not show up, try having a friend (with a working reader) format the card on their computer and try again.

Skip to the end of this answer for an explanation of this process.

As far as USB card readers go, they can malfunction for a variety of reasons that may or may-not be related to the reader itself. Here are a few steps for troubleshooting the reader:

  • If the card reader is connected to a USB hub, try connecting it directly to your computer.
  • If the reader is already directly-connected, try using a different port*.
  • If the reader has a detachable USB cable, try swapping it out for another.
  • Lastly, try using the reader on another computer.

If all these steps fail, it may be time to pickup a new card reader.

(*USB ports often come in pairs, if possible, connect to another port as far away from the one you’ve been using as possible.)

Formatting the card (which is different from deleting all images or 'clearing' it) is a process that prepares the card to store files, by establishing a file system. Removable media, like sdcards or USB flash/thumb drives, occasionally end up with errors in the file system on the card. The most common cause of such errors, is a card being 'removed' (unmounted) incorrectly e.g., a card is taken out of the reader, while the computer is still accessing it.

It is possible for your sdcard to function inside the camera, but to be unreadable on your PC, when such file system errors occur. (Re)Formatting the card will effectively erase all data on the card and will re-create the necessary file system.

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There could be quite a few problems that would cause SD cards not to be read by a computer:

  • Check the metal leads of the card and wipe it off with a clean surface. There may be some sort of oil that could be preventing your computer from reading the card.

  • The problem may also be with your SD card reader on the computer. Try using a different card and see if any thing happens.

There should be no reason to worry about the cards if they continue to work on the camera, but if you can't get these solutions to work, use a different card.

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We go through a lot of SD cards at my work, and so I've seen many cards fail in different ways, from the occasional fried controller (not the problem you're having since the card would have stopped working altogether) to bad blocks to simple filesystem errors. I've also seen SD cards that were slightly-out-of-spec that work in some card readers but not others (to top it off, it was a batch of cards that had the same serial numbers as the "good" cards from that manufacturer, but had been manufactured in a different facility!).

So the first thing I'd suggest is to try your SD cards in multiple readers. It's possible that the card is just a little bit out-of-spec (either due to manufacturing errors or as a result of its environment), or that the hardware of your card reader is slightly out of spec, or the card and reader are both in spec, but at opposite ends, and just don't quite work with each other.

The card could also be starting to go bad. I don't know how other OSes do things, but on Linux (I assume OS X is similar enough for this to be useful there, too) when the OS can't read part of an SD card it tries again a few times, then tries reading a smaller section of the card a few times before it gives up. If you're using Linux, I'd take a look at the system logs (/var/log/syslog or messages, or do a 'dmesg | tail -20' or so) to see if you can get any useful information about what the OS is trying to do. If you see that the OS is trying several times to read the card and eventually giving up, you could also try again. I've seen cards that have to be re-inserted into the card reader two or three times before they work (though I think that when I've seen that, those cards eventually "get worse" after a while and stop working altogether, so if your SD card regularly requires 2 or 3 attempts to read it, I'd replace it as soon as possible).

I don't know what cameras do when they read SD/CF cards, but they seem to load them a lot faster than I would expect. Either the camera's firmware does a really good job of running critical tasks in the background or the firmware doesn't fully read the SD card. If the latter, it's possible that your SD card has failures that the camera isn't aware of, but that are severe enough to prevent your OS from reading the card. I'd suggest formatting the card in your camera (if you have multiple options, like 'quick' and 'full', do whichever one takes longer: I'm hoping that will cause the camera to actually read and, hopefully, write to each block of the card -- and become aware of any errors it isn't seeing in normal use).

If formatting the card allows you to read the card in your card reader, I'd try to find a way to search for bad blocks/sectors/anything else on the card. With SD cards, the controller is supposed to abstract away things like bad blocks, but there may be ways to look for them (I kind of doubt it, though I did find this answer).

If you can, I'd also try taking enough pictures, that you don't mind losing, to completely fill up the card. Then get them onto your computer and make sure there are no errors. This won't prevent the card from failing in the future, if it's already on its last legs, but it might give you some confidence that you can read any picture the camera can write to the card.

However, if you format the card and still can't read it on your computer using multiple card readers, and you can afford it, I'd replace the card. I'd be very concerned that the card is damaged and in the near future either it will fail completely or the camera will blindly write pictures to bad sectors.

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I had this problem with my older (T1i) Canon camera: It wouldn't always work with some SD cards. Fixed it thus: dipped the connector end of an SD card in Vaseline (only as deep as the contacts). Then wiped the Vaseline off with toilet paper. Inserted the card a few times into the camera. No more problem.

Theory: Corrosion on the camera contacts. Sliding a chip in several times knocked the corrosion off, and the residual Vaseline prevented the problem from coming back. YMMV, but I think this is unlikely to do harm. I did this instead of replacing the camera since it's hard to get "unreliable" problems fixed.

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