Storage Card Practices

The following are basic practices I believe all digital photographers should follow with their card storage strategy, as well as information about how images and information is put on cards. Ignoring any of the practices or not knowing the structures can lead to troubles, the worst being loss of images. You don't want to lose images, do you?

On Buying a New Camera

Buy a set of the fastest cards made for the highest end technology that the camera uses.

For instance, the Z50II was designed for UHS-II SD cards, so you should buy some new UHS-II SD cards when you buy that camera. The tricky part is understanding just how fast a card is "optimal" for a new camera. Your camera will never get faster at writing to cards, but you don't want to make it slower by using suboptimal cards. If faster cards become available after your camera came to market, it's unlikely that your camera will speed up if you use cards with that newer technology. However, if in doubt, just buy the highest speed and latest technology available. That way if you end up with a faster camera later, you'll be ready.
Cameras often operate as slow as the slowest card in them. That applies both to buffer and image review performance. That's why you don't want to put a UHS-II card in one slot and an old, pre-UHS card in the second slot of a two-slot SD camera. Even if you aren't writing to both cards simultaneously, image review performance often will be triggered to the slowest card. Why? Because cameras do FAT/Directory checks on all cards when you press the playback button; older cards will slow that process. Note that some cameras have one "fast" card slot and one "slower" card slot. If you use two cards in those cameras, some camera operations will be only as fast as the slower slot.
- So: if you want fastest performance from your camera, use only one fast card in the faster slot. I did this all the time with my D500: the XQD/CFe cards were about double the speed of the fastest SD cards at the time, so I simply photographed with only an XQD/CFe card in the camera most of the time. These days, the same is true for my Z8: a fast CFe card only in the first slot, nothing in the SD slot.
Some camera functions slow with the largest card capacities. This has varied over time and with card type, but there have been "sweet spots" in performance well below the largest capacities. For example, 32GB SD cards tended to be faster to save images than 128GB SD cards. This was due to some overhead in managing the additional chips in the higher capacity cards. The opposite is now true for CFe cards: the 1TB cards tend to be faster than the 64GB cards because the card itself uses multiple chips simultaneously on the larger card. If there’s a loss of speed it usually isn't severe, but if you're trying to maximize buffer performance, think smaller SD card, not bigger, but bigger CFe card, not smaller. Unfortunately, there's a lot of variability in this, so you have to experiment to find what size is fastest with your card and camera vendor.
- There's also a slowdown when reviewing images on large capacity cards, or even pulling up the menu system on some cameras. That's because those cameras are doing a check of the FAT and directory on the card each time you press PLAY or MENU. The larger the card capacity, the longer the integrity check takes. So you might see a very brief delay with a 64GB card, but a longer one with a 1TB card.
- If speed isn't important to you, consider buying lots of older, less expensive cards and just using each one once (much like film, they become your "original" after being taken out of the camera, and you just build an archive of taken images stored on cards). Certainly with SD cards, a wallet of such cards isn't particularly big, but can provide a simple "back-up" system while traveling.

Erasing Images Best Practices

Erasing images is when your data is must vulnerable. Gone are the days when the digital cameras had OS errors that "accidentally" destroyed files, but that doesn't mean that you still can't lose a file.

Always use Format in the camera to fully erase cards prior to each use. Yes, there are some subtle differences in how the camera makers think the card is formatted, thus their formatting procedures should always take preference over others (see low level format below, though).
Minimize your use of deletion of images in camera, and be particularly wary of doing this as your card gets close to being full. In-camera deletion used to be a very big issue, as the file management within many early digital cameras was highly suspect. Over the years the biggest problems were fixed, but the issue with file deletion is that it is telling the system which sectors are free to write to, and as you do that you start fragmenting where data is placed on the card. File fragmentation is a silent data killer, as images do not have fixed sizes, so the next image you take doesn't fit exactly in the spot you opened up. Over time, if you aren't formatting your card (see the previous bullet), fragmentation can become very problematic for performance, and it can become lethal as you near filling a card with images.
If you connect your camera to a computer or put your card in a card reader connected to a computer, be wary of programs that "touch" the file structure of the card or write files to it. You generally don't want your computer to build a file index on your cards (e.g. Spotlight on Macs), for instance. While an in camera format should remove it, there are programs that write files to storage that are invisible or protected, and that can become a problem. But the big point here is similar to the previous ones: if you have your ingest program "delete all files after ingest," you've got something writing information to the card and changing data in the FAT and directory. You don't want that. Only the camera should be writing information to a card (or changing it).

Card Failures

If you encounter a card that has a problem, sometimes a low level format is what is needed (to eliminate bad sectors and restructure the card the way it was shipped). For SD cards, the answer is simple: use Panasonic's card formatter. Also available at SD Association. This utility is the one to use to restore any SD card to the way it (should have) shipped from the factory.

CompactFlash, CFast, XQD, and CFexpress don't have any such a generalized utility, so you're going to have to use an OS utility and get the parameters right (exception: Nikon Z9 generation cards that use CFexpress now have a Full Format option you can use in the camera; more on this in a bit). Here are the parameters you should use for an OS-based format:

Card is less than 128GB: FAT32 (sometimes called MS-DOS file system or similar)
Card is greater than 128GB: exFAT
Partition scheme: Master Boot Record

Card failures happen. More often than camera failures. The most typical symptom of a card failure of some sort is you see the image correctly on the camera's LCD (because you're looking at the embedded JPEG preview) but when you go to work on the raw file (or even the full JPEG) you get bands of color, usually across the bottom of the image. This is an indicator that the full file data didn't get written to the card correctly, and often happens when the camera's write mechanism is stressing the card (i.e. when you're taking long bursts of continuous images).

If all your cards produce the same problem, suspect the camera. Have it looked at for a card write mechanism failure.
If only one of your cards produces this problem, suspect the card. Do a low-level format (see above) and try again. If the problem persists, retire the card, it may have bad NAND cells or broken memory management.

Folder and File Structures

It's important to understand the folder structure on the card and how your computer/software sees it. For still images, there will always be a DCIM folder (Digital Camera IMages) at the root level on the card.

Inside the DCIM folder may be one or more folders created by a camera or cameras (e.g. if you moved the card between cameras). Since a folder should only have 999 images in it by the original standards definition (this has been increased to 5000 by some makers, and the absolute maximum is 9999), if you take a lot of images, you'll have multiple folders on the card. If you are manually moving images to your computer, this is important to note: you may have to move images from multiple folders to your computer or else you will lose images! Even some automated software gets this wrong (particularly if it detects differences in the sub-folder naming). So always verify that all images on the card got transferred.

Note that if you move cards between cameras, you get differently named folders inside the DCIM folder. You may also get additional folders on the card that only one of your cameras recognizes. Generally, I don't recommend moving cards between cameras, and I strongly don't recommend moving cards between camera brands.

Outside the DCIM folder there may be other files the camera has written. Things like Settings files, for example. It's important that you understand all the files that your camera can create and where it puts them (I have an article on zsystemuser.com that defines all the files that current Nikon cameras make).

Many cameras put non-image files outside the DCIM folder. So if you wanted to save those files, you'd need to transfer them manually.

For video images, some cameras store them in the DCIM folder, while other cameras (e.g. Sony) use the AVCHD standard, which creates a complex folder structure that was originally defined for DVD and Blu-Ray players, and the actual "video" file is buried deeply in that (the actual video "clips" are in root/PRIVATE/AVCHD/BDMV/STREAM).

Summary

Buy new cards for any new camera, and make sure they match the camera's top capability.
Always format cards in the camera.
Minimize your use of file deletion on a card.
Understand the folder and file structure that your camera creates so that you now where the data you need to transfer is on the card.
If you suspect a faulty card, do a low-level format on it and test the card before using it for taking images again.