Are there any disadvantages to using a single microSD card in multiple devices?

... for example, in a digital camera, a tablet and a cellphone, all of which have cameras on them and will be storing images on the card.

I'm asking not from a mechanical standpoint (assume the card will not be damaged in moves from one device to the other) but from a software one. From my understanding the common DCIM directory should appear with its subdirectories for each of the devices, and they should not interfere with one another's data.

Apart from filling the card to the very top, which should be avoided judging from some of the answers here, are there any other pitfalls which might result from this approach?

• The biggest problem I see is that the card isn't in device X when that's the one you want to take a photo with. Given the price of SD cards, why not just buy 3 of them? – Philip Kendall May 7 '14 at 21:36

Each device will want its own set of folders in the root directory to handle its files. Some are ok with other folders being in the root directory but most are not. It is ok to use the same microSD or any other format card in any and all devices as long as it is formatted by the device that you want to use it in prior to each first use.

Looking only at digital cameras, some of them may only browse within the directories they have created (and understand), or they may allow the user to freely choose which directory to browse.

I see three possible scenarios here:

1. Camera does not recognize the "foreign" directories
• Con: You wouldn't be able to browse through all the photos
2. Camera picks up all the pictures under DCIM directory, and shows some 'unsupported error' for photos not taken by the camera
• Con: Makes browsing harder (you have to keep skipping through these 'unsupported photos')
3. Camera picks up all the pictures under DCIM directory, and actually renders them well enough (say, as long as they are under certain dimensions)

Besides photos, I think some cameras do create extra files for indexing purposes. This shouldn't be a problem across brands (that do this), but if you're using the same card for two different products of the same brand, you may want to take note of this too.

In the earlier days of digital cameras not all devices wrote filesystems the same (or correctly), so this could have been a problem. With newer devices this seems to be folklore.

Having said that, the safe answer is whenever you insert a card to use in a device, format it in that device. That's the most reliable way to make sure there aren't lingering compatibility or corruption problems when you start using a card. It also is a good habit to prevent the problem of forgetting there's already data on a card and using it thinking its empty, only to run out of space in the middle of a shoot.

A side advantage of this is that the images stay on the card until next use, so if there's some kind of processing problem where you need to recover an image or re-import the images, they aren't deleted until the next time you use that card. A quiet, temporary spare copy backup, just in case. I've only needed that once in the last ten years, but boy, when I needed it, I was glad it was there.