I have a Canon Rebel T7 and a recently-purchased "onn."-branded MicroSD card with an adapter.

I purchased this memory card in preparation for vacation, and the first time I used this card (besides a test shot or two) was for an overnight timelapse (using an external intervalometer). (This was several days into the vacation, and I was starting to fill up my other SD card which I had been using.) I set up the timelapse in the evening, and when I came out in the morning, the battery had died (which was not unexpected). When I put in a fresh battery, however, the camera displayed a "Card cannot be recognized, please format card" message. I popped it into a Windows computer and got the "File system not recognized, please format card" message. Fortunately I've heard about photorec and had another SD card with me, so I removed the unreadable card from the camera and was later able to recover the images with photorec. I assumed that the battery must have died in the middle of writing and image to the card, which somehow corrupted the filesystem structures. So I didn't think much else about it once I had recovered the photos.

After re-formatting this card, I took some "regular" (not timelapse) photos and one timelapse during the day (where I was able to monitor and replace the battery as needed), and had no issues, all with the "onn."-brand microSD card.

However, the other night I set up another timelapse on my front porch using the same setup and microSD card. When I came out in the morning, the battery was still full and the camera displayed the same "Card cannot be recognized, please format card" message. Windows also was unable to recognize the filesystem. Another round with photorec seems to have recovered all of the images that were captured - everything that was on the card before the timelapse (including the previous daytime timelapse), plus about 100 images of the overnight timelapse itself.

At this point I started suspecting that the microSD card had bad blocks or some other corruption, so I formatted the card in Windows and ran MediaTester on it. However, MediaTester found no errors.

What should my next steps be to identify the issue? I'm suspicious of the microSD card, but the media tester didn't find any issues with it. I've had this camera for over a year and (until purchasing this new microSD card) have only used the 64GB SanDisk SD card that was bundled with the camera (and have taken many timelapses with no problem). If the microSD card is bad I'll definitely throw it out, but I'm wondering if there could be an issue with the camera at play here?


1 Answer 1


Throw the MicroSD card. Or use it for something not important as MicroSD, not with adapter. Adapter is other device (passive but intermediate) and can cause some unpleasant side effects. Your camera is for SD cards so buy SD card and use it.

The problem with camera can be caused by battery not keeping the charge (battery with end of charging resource, usually you can count for 200-300 changers per battery). Try with new battery, freshly charged.

And do not forget batteries and storage cards are consumables and over the time must be replaced.

  • 1
    \$\begingroup\$ Ah, I hadn't considered the adapter playing a part -- for the test, I just used the microSD slot in my card reader. I'll just do that then (though maybe run the test with the adapter for kicks and giggles). Thanks! \$\endgroup\$
    – maples
    Commented Oct 9, 2021 at 21:27
  • \$\begingroup\$ I had more problems with the actual full size SD cards still being made than with adapted MicroSDs.... \$\endgroup\$ Commented Oct 10, 2021 at 16:49
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    \$\begingroup\$ @rackandboneman, check your cards. I own and use more than 30 SD cards (from reputable manufacturers ) and had problem (with few files only) only once. \$\endgroup\$ Commented Oct 10, 2021 at 17:12
  • \$\begingroup\$ Agree with @RomeoNinov. I use only Sandisk Extreme or above. The Extreme Pro cards with 100MB/s write times are ideal for day to day professional use. I've tried a fast Micro SD + adaptor combo and found it's almost 3x slower then using proper cards. Micro SD adaptors will slow down the write times, and this makes them more susceptible to issues - more likely for camera to turn off whilst writing to the card for instance. \$\endgroup\$
    – AutoBaker
    Commented Oct 25, 2021 at 9:31

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