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The reason I ask is that I recently attended the LA Photo Show and the SanDisk rep there told me that swapping memory cards between different cameras is a very bad idea. He told me that the reason is because it will lead to disc corruption and dramatically reduces the life of the memory card.

Previously, I have done this (swapping between devices) many times, always formatting the SDXC card, after placing it in the new camera, just as a precaution. My experience comes from way back when I used to format my 1/4" floppy discs when using them in a different PC, as a way of making me feel that the disc is going to read/write ok, if the format worked smoothly.

I realize that I should probably just accept the SanDisk product reps advice, but I was wondering if there are any studies or documentation to support this? I have Googled it and can't really find anything substantial. Most cameras create their own folders with different names, but these files are created automatically on a newly formatted card when the camera is turned on for the first time, after the formatting.

I have several large and expensive Pro Extreme SD memory cards and several digital cameras (Canon T3i, Canon 5DM3, etc), so this concerns me.

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    If you do not reformat it could lead to problems, but if you reformat when moving to a different camera there should be no issues (assuming you have already copied the content that gets erased when you reformat). – Michael C May 31 '14 at 18:38
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With most cameras, not much actually changes on the memory card, when being formatted, other than the pointer to the file being erased. On the other hand, some cameras like the Canon 5D Mark III, allow for a low level formatting option, which should help a lot. The answer is that lots of people swap memory cards all the time and don't have problems, but they could happen due to file corruption in some rare cases. I think that if your camera allows for low level formatting, you should be ok, otherwise its better to be safe than sorry and not swap them.

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    Why would low level formatting matter, let alone "help a lot"? – mattdm May 31 '14 at 3:02
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    A bit more research found this information: Low-level formatting does a better job of erasing the files. Exactly, what level of difference is a gray area. The low-level format marks 'bad' sectors and takes them off limits for future use, which is helpful, and in the case of a badly corrupted card, 'help a lot'. – Vonada Jun 3 '14 at 23:20
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    @Vonada The card's firmware does that at a level invisible to the camera or any other operating system. – mattdm Nov 3 '18 at 17:36
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    The only meaningful effect of low-level formatting for a flash card (apart from making the data unrecoverable) is improving write performance by pre-erasing all the flash blocks. – dgatwood Dec 7 '18 at 20:07
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    I want to stress again — "low level formatting" is a concept from now-ancient storage technologies. There is no low-level format of SD cards. The card's own firmware is responsible for wear leveling and for relocating bad blocks. So this answer is, unfortunately, misguided. – mattdm Dec 21 '19 at 14:26
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It is okay to do this. The advice you were given is superstition that doesn't have any technical basis. (Cynically, the memory card manufacturer's representative may just have wanted to sell you more cards, and to propagate a story which could lead to more sales if widely believed.)

This is slightly related to What is the right way to format a SD Card for use in camera? — another place where people often warn not to do something which is probably no big deal.

The filesystem used in almost all cameras is FAT, which is relatively simple and well-understood because it is so old and used pretty much everywhere. Every embedded operating system which might be used in a camera will have this tested and retested and proven by experience. There may be remaining driver bugs, and it's conceivable that some interaction between bugs could cause problems, but most such bugs are really worked out by now, and the interaction seems quite unlikely. And especially if you reformat in the new camera each time... really, there's very little mechanism for anything to go wrong.

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  • A potential exception is Sony cameras, which use an on-card database to track images. The database is not updated when images are managed by other cameras or software. Formatting the card fixes the problem as a side effect by forcing the database to be reset. The same can be accomplished by deleting the database files. – xiota Oct 26 '19 at 4:30
  • Also, OP describes owning multiple Canon cameras. I recall someone commenting elsewhere on this site that Canon cameras have some filesystem bugs. I've also had issues with cards being reported as unformatted or unreadable when moved between Canon and other cameras. In my case, the problem was solved by a single in-camera format, and there was no need to repeatedly reformat the card when moving it among cameras. – xiota Oct 26 '19 at 4:39
  • @xiota given that most cameras stay out of each other's DCIM folders.... – rackandboneman Oct 28 '19 at 12:01
  • @rackandboneman When writing new images, not when viewing and deleting images. Also, it doesn't matter what folders are used with cameras that have buggy filesystem drivers. – xiota Oct 28 '19 at 16:52
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    As noted, I'm pretty skeptical about the fear of buggy FAT drivers. Or even exFAT. A comment on this site that someone thinks there is a bug is not very strong evidence to me. – mattdm Oct 28 '19 at 17:00
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This sounds like the Sandisk rep wanted you to buy more cards :). No reason why this would cause problems, and you are doing the right thing by formatting the cards before using them in different cameras. Memory cards are pretty cheap, though, so for convenience it might be worth having dedicated cards for each camera.

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It is no problem to reuse cards between cameras.

However, cards have a write cycle, meaning each page (part of a card) can be written maximum a number of times. However, this amount is a lot (like 100,000).

When you write a picture, only the number of pages are written containing the information/file of that picture. However, luckily there is also wear leveling (see https://en.wikipedia.org/wiki/Wear_leveling) built in, meaning that the SD card distributes the writes over the SD card, so even if you overwrite the first file, it will end up on different pages. See also dgatwood's remark below for more info about wear leveling.

If you do a low level format, all sectors are written.

But even then, it really does not matter if you write the pages in camera X or camera Y.

Reading from an SD card does not even deteriorate it at all.

Only physical damage can be done if you damage the card BECAUSE of taking it in or out a camera.

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    If you overwrite a file, you're almost guaranteed that the new data will be on different pages, unless all the bits just happen to flip in whichever direction doesn't require an erase (rare). What's kind of hard on cards is keeping some data on them permanently, and only reusing part of the card. Most flash cards do only dynamic wear leveling, i.e. blocks that don't ever change also don't ever get returned to the free pool even if other blocks are on the verge of dying, which means that reusing only part of the card can result in very uneven wear levels. – dgatwood Oct 25 '19 at 22:59
  • @dgatwood Thanks for your comment (I mentioned it explicitly in my answer, with your name for credits). – Michel Keijzers Oct 25 '19 at 23:33
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Previously, I have done this (swapping between devices) many times, always formatting the SDXC card, after placing it in the new camera, just as a precaution. My experience comes from way back when I used to format my 1/4" floppy discs when using them in a different PC, as a way of making me feel that the disc is going to read/write ok, if the format worked smoothly.

Wrong reason, right action. With PCs, basically all of the PCs share the same operating system code and/or have it extensively tested for compatibility. The reason to reformat floppy disks is differences in head alignment. That's the same reason that on good quality tape drives, playback results are usually best using the same tape drive that you started with.

Now SDXC cards, as opposed to floppy disks, come with their own controller and talk only digitally/electrically to the camera/cardreader. There is nothing even remotely similar to the head alignment thing of magnetic media.

Instead, the problem may lie with a camera-internal operating system that implements the format in question in its own way, and there will be at best minuscule amount of testing involving third-party devices writing on the media.

Camera file data tends to be organized in a very straightforward manner for any given camera. If a camera takes stupid shortcuts (or has buggy code not working with all preexisting structures) like relying on some initial directory hierarchy being created in certain places on the medium or allocating new files in a different manner than standard on the file system, or is unhappy with file names looking significantly different from what it would create itself, having multiple devices (including cardreaders!) write to the medium in alternation can cause trouble.

This is even more likely with SDHC cards and earlier which use the FAT/VFAT file system (with the camera only needing FAT style file names but VFAT being often used by general purpose computers to allow for file names and directory hierarchies not supported by the original FAT). Or with early cameras supporting SDXC (it's not like the Exfat file system is so very old).

So while reformatting might take a hit on the read/write cycles of a card, it's a reasonable paranoia reason. Taken to some more extreme paranoia, you'd never edit, delete, or store anything on the card using a card reader (including the camera in mass-storage mode), making sure that only the camera is allowed to change the card.

I don't do that. And so far I've not been bitten by camera problems, the worst being some, uh, Casio? camera with xD memory cards putting on a file system crashing my (Linux) Laptop. That was irritating.

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If you do not reformat it could lead to problems, but if you reformat when moving to a different camera there should be no issues (assuming you have already copied the content that gets erased when you reformat).

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  • What problems might not reformatting lead to? – mattdm Dec 21 '19 at 14:27
  • @mattdm The one discussed in the first comment to this answer, for example. – Michael C Dec 22 '19 at 4:18
  • But that's only a problem if software tries to mess with the Sony images. That's unlikely because of DCIM. – mattdm Dec 22 '19 at 4:46
  • That's why I used the word could, rather that will. It could happen under certain specific camera combinations and practices. – Michael C Dec 22 '19 at 6:00
  • @mattdm There is some room within the DCIM standard for manufacturers to do things inside the DCIM folder slightly differently than another in terms of including additional folders with specific information in them. – Michael C Dec 22 '19 at 6:04
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I lost 2 lexar 64GB memory cards from swapping from Sony to Canon (formatting them each time). I don't know if it's a problem with Lexar memory cards, but considering the price, I think they aren't that good. I would not advise swapping in my experience. There's probably nothing proven or facts out there, but just sharing the experience. I think as someone mentioned it's safer to buy dedicated memory cards.

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  • Older cameras may not be able to handle 64Gb cards. That might be a problem. – Chenmunka Oct 25 '19 at 15:07
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    What do you mean, lost? It's a storage device - format it and move on. As mentioned above, it's possible older cameras won't play with it due to the size but if they're current cameras, you should be good. – OnBreak. Oct 25 '19 at 22:03

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