A memory card is easy to overlook until a slow one stalls your camera mid-burst or a failed one loses a shoot. Choosing well comes down to three things: the right type and speed for your camera, sensible capacity, and reliability. Matching the card to how you actually shoot matters more than buying the fastest or largest card on the shelf.
Start with the type your camera takes. Most cameras use SD cards, while many professional bodies use the much faster CFexpress, and older models may use CompactFlash or microSD. The camera manual lists supported types, and putting a slow card in a fast camera wastes the camera’s capability.
Understanding speed ratings
SD card speed is marked with several overlapping symbols, which is where the confusion starts. The UHS bus is shown as a Roman numeral I or II, and the sustained write speed is given by the Video Speed Class, V30, V60, or V90, meaning 30, 60, or 90 megabytes per second guaranteed. Write speed is what matters for clearing the buffer after a burst and for recording high-bitrate video without dropping frames. The headline read speed on the package is mostly about how fast you offload files to a computer.
Capacity and reliability
On capacity, several smaller cards beat one huge one for safety, because a single failure then costs you only part of the shoot. A 64 to 128 gigabyte card suits most stills photographers, while video and high-resolution burst shooters need more. Buy from reputable brands through reputable sellers, since counterfeit cards with faked capacity and speed are common on marketplaces.
Treat reliability as a habit, not just a purchase. Format cards in the camera rather than the computer, replace them every few years, and offload and back up before you reformat. If your camera has two slots, set the second as an instant backup so every frame is written twice. Pair this with a sound file management routine and you remove most of the ways a card can cost you images.
Common mistakes to avoid
- Buying for headline read speed when sustained write speed is what clears the buffer and sustains video.
- Using one giant card, so a single failure loses everything from a shoot.
- Buying cheap cards from unknown sellers, which are often counterfeit.
- Formatting in the computer instead of the camera, or forgetting to back up before reformatting.
Frequently asked questions
What speed memory card do I need?
For general stills, a UHS-I card rated V30 is plenty. For fast continuous shooting and high-bitrate or 4K video, choose V60 or V90, or CFexpress if your camera supports it. Match the rating to your camera and your subject.
Is it better to use one large card or several smaller ones?
Several smaller cards are safer, because a single failure costs you only part of your work. Very large cards make sense mainly for long video recording.
How long do memory cards last?
Cards have a finite number of write cycles but usually last years of normal use. Replace them every few years, retire any card that throws errors, and never rely on a card as long-term storage.
Backing up in the field
A card is working storage, not a backup, so build a habit of getting images off it safely. If your camera has two slots, set the second to record a duplicate of every frame, which protects you instantly against a single card failing. On location, offload to a laptop or a portable SSD at the end of each day before you reformat anything, and keep your cards in a small case rather than loose in a pocket. Format in the camera when a card is empty and verified backed up, never midway through a shoot, and retire any card that has ever thrown a read or write error.