You may have hit a corrupt block on the disk that hadn’t been used before.
Reformat the card (always only format cards IN CAMERA ... never on the computer ... this assures that the exFAT filesystem is created with the blocking factor that the camera is most efficient at using)
Also... even MORE important... make sure you check the “low level” tick-box when you do the format. If you do “low level” then the camera actually create and checks every block on the filesystem. If you do NOT do “low level” then the format simply reinitializes the filesystem info without actually writing out each block.
You WANT that write because when the camera writes it, it checks to make sure the write succeeded and it will “map out” any bad blocks to avoid using them in the future.
As for “too much” card.
You want a card that matches the capabilities of the camera’s card slot. For example, I have a 5D IV. It takes both CF and SD cards. But the very very fastest CF card technology is called “CFast” but the 5D IV doesn’t actually have a “CFast” slot. You can “use” a CFast card... but it forces the card into “compatibility mode” to work as a normal CF card (which isn’t nearly as fast as a native CF card). So you actually get WORSE performance by buying a HIGHER end card and forcing the high-end card to work in a “compatibility mode”. You really want the card where the card is in it’s “native” mode when used in that card slot.
If your 80D (because I’m not looking at the specs as I write this) is a “UHS-I” slot... then use a “UHS-I” card. But don’t use a “UHS-I” card in a slot for a camera that only supports.... say “Class 10” SDXC cards that aren’t technically “UHS-I” because this forces the card into “compatibility mode” where it wont be nearly as fast as a native card.
Compatibility mode shouldn’t result in corruption... just slower performance. Corruption is a different problem. The most likely cause of corruption is a bad block on the card itself. The process of “writing” to non-volatile flash memory is technically moderately destructive (which is why cards have a limited number of “write” cycles before they are predicted to fail.)
Think of cards as being like the tires on your car. Each time you take a trip, that tire does technically wear. A trip to the local grocery store may be an imperceptible amount of wear that you can’t measure in just one trip... but rest assured the amount of wear was not “zero”. After enough tens of thousands of miles... you eventually need to replace the tires.
Memory cards work the same way. They do “wear” when used... and will eventually need to be replaced.
The amount of use for casual users is so little that it’s likely you’ll want a newer model camera before the card fails. But if you use the card quite heavily... the card may fail before you want to upgrade the camera.
Tim Campbell
5D III, 5D IV, 60Da
