The card is the cheapest part of your kit and one of the easiest to get wrong. Here is how to read the label.
Card families
SD cards are the most common in mirrorless cameras. The size class tells you capacity: SDHC covers up to 32GB, SDXC covers above 32GB up to 2TB.
CFexpress cards are faster and used in higher-end bodies. Type B is the larger format and Type A is smaller. They have to match your camera’s slot. They are not interchangeable with SD.
Reading the speed marks
UHS bus. UHS-I is the common standard. UHS-II adds a second row of pins and much higher maximum speeds, if your camera supports it. The camera’s slot sets the ceiling.
Speed class. U1 guarantees 10 MB/s sustained write and U3 guarantees 30 MB/s.
Video speed class. V6, V10, V30, V60 and V90 guarantee 6, 10, 30, 60 and 90 MB/s sustained write.
What to buy
- Stills and casual video: a V30 SDXC card works for most cameras.
- High-bitrate 4K and 6K video: check your camera’s manual. Many high-bitrate modes need V60 or V90 cards.
- Burst shooting: read-and-write speed affects how quickly the camera clears its buffer, so a faster card can help.
- CFexpress cameras: buy the exact type your body lists.
Habits that protect your work
- Use several smaller cards instead of one large card.
- Format the card in the camera before each shoot.
- Do not delete files on the card. Offload, verify, then format.
- Buy from authorized retailers to avoid counterfeits.
Frequently asked questions
What does V30 mean on an SD card?
V30 means a minimum sustained write speed of 30 MB/s, which is enough for many 4K video recording formats.
Can I use a UHS-II card in a UHS-I camera?
Yes. It works, but runs at the slower UHS-I speed.
How big a card do I need?
For stills, 64GB to 128GB holds a long shoot. For high-bitrate 4K video, 256GB or more is common. Use several cards instead of one giant one.