Memory cards: choosing, formatting and handling them safely
Match card speed to your camera's needs, size cards so one failure is survivable, format inside the camera and power down before removing a card.
Four common habits lead to lost footage on memory cards: a card too slow for the recording mode, a whole trip stored on one card, formatting before the files are copied, and removing a card while the camera is still writing. Each of these habits is simple to change, and changing them protects the footage you care about most.
Card problems rarely announce themselves until the moment you need the footage. A card that stops recording halfway through a clip, shows a generic error message or fails to show files on a computer may already be struggling. Treat any unexplained error as a warning and deal with it before the next important shoot.
Read the speed ratings before you buy
Card markings tell you how fast the card writes data, which matters most for video. The camera manual lists the card class it expects for each recording mode, and that recommendation is the most reliable guide. A faster card will not improve a slow camera, and a card slower than the recording mode needs can drop frames or stop the recording.
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| Marking | Minimum sustained write speed | What it suits |
|---|---|---|
| Speed Class 10 | 10 MB/s | Basic full HD video and photo bursts |
| UHS Speed Class U3 | 30 MB/s | Many 4K recording modes |
| Video Speed Class V30 | 30 MB/s | Standard 4K video |
| Video Speed Class V60 or V90 | 60 or 90 MB/s | High bit-rate 4K and high frame-rate recording |
Check the bus type as well. A card that supports the faster UHS-II standard gains speed only if the camera supports it, because the slower of the two sets the real performance. Buy from reputable retailers. Cards from unfamiliar sellers that are much cheaper than the usual range, or that advertise capacities no real card has, are often counterfeit and may record data incorrectly.
Choose a capacity that limits what a failure can cost
Bigger cards hold more footage, which is convenient, but a single failure then puts a larger share of your work at risk. Splitting a shoot across two or three smaller cards keeps one problem from wiping out everything. A card that holds about one day of work is a practical target for most hobbyists.
File size grows quickly with video. A 4K recording at 100 megabits per second uses about 12.5 megabytes per second, or roughly 45 gigabytes per hour. A 128-gigabyte card holds less than three hours of that footage. Bit rates vary by camera and setting, so check the file size estimate in your camera's manual or menu before you plan a shoot.
Copy footage to a second place as soon as possible after each session, and keep the original card until the copy has been checked. Only then should the card be formatted and reused.
Format the card inside the camera
Format cards in the camera rather than on a computer. Formatting in the camera creates the folder structure and file system the camera expects, which reduces the chance of files it cannot read. Do this only after you have copied and checked everything, because formatting erases the card's file index. Formatting after each finished project is also more reliable than deleting files one at a time.
Choose the correct file system in the menu when the camera offers the option. Cards up to 32 gigabytes are usually formatted as FAT32, while larger SDXC cards use exFAT, and most cameras set this automatically. Some cameras also offer a full format, which overwrites the whole card and takes longer than a standard format. It can help restore write speed on a card that has slowed down, but it does not usually report faults, so a card with repeated errors still needs replacing.
Remove and insert cards without corrupting files
Power the camera off before removing a card. Pulling a card while the camera is recording or writing can leave a partly saved file, and the access light on most cameras shows when the card is busy. Wait for the light to go off, switch the camera off, and then open the slot.
When you read a card on a computer, eject it through the operating system before unplugging the reader or pulling the card. Removing it while the computer is still copying can damage files and the card's structure. Handle cards by their edges, keep them in a case, and store them away from heat, moisture and static.
If a card refuses to record, check the small write-protect switch on its side before anything else. A switch in the locked position stops the camera from saving new footage, and that is a quick fix rather than a fault.
Recover from card errors without making things worse
When the camera reports a card error, avoid repeated, hurried attempts. Power the camera off, reinsert the card firmly and power on again. If the error continues, try the card in a different slot or reader, or in another camera of the same type, so you can tell whether the fault lies with the card or the camera.
If files are missing or the card cannot be read, stop writing to it. Do not record new footage, take photos or format the card, because new data can overwrite files that recovery tools may still find. Recovery software can sometimes read a card the camera cannot, but results vary. For footage that matters, a professional data recovery service is the safer option.
Replace any card that shows repeated errors, even after formatting. A card that has failed once may not be reliable again, and the cost of a new card is small compared with a lost shoot. Labeling each card with a number or letter helps too, because it shows which card held a problem clip and which camera it came from. Rotating the cards through your shoots spreads the wear, so no single card takes every recording.