Memory Cards Explained

The Numbers & Symbols on Your Card Explained

Take a look at one of your memory cards – do you know what all of the numbers, terms and symbols on the card mean? Everything may be clear if you’re an experienced photographer or videographer, but for beginners and first-time users, some things may need clarification. It may seem like A LOT to learn, but it’s all actually quite simple. Here, we’ve broken down the common terms and symbols found on a memory card in order to help you understand which cards are best for certain cameras, as well as make a careful and informed purchasing decision.
CAPACITY:
  • SD / microSD: Up to 2GB
  • SDHC / microSDHC: From 4GB to 32GB
  • SDXC / microSDXC: From 64GB to 2TB
  • CompactFlash: Up to 512GB
  • CFast 2.0: Up to 512GB
  • XQD: Up to 240GB
  • CFexpress™ Type B: Up to 2TB
MAXIMUM READ SPEED:
The fastest speed that data can be transferred from the card to a computer. The higher the read speed, the less wait time and sooner post-production can begin. High read speed is ideal for photographers and videographers who need to quickly unload large amounts of data and get back to shooting.
MAXIMUM WRITE SPEED:
The fastest speed that data can be written to the card. The higher the write speed, the more you can capture in a certain amount of time. High write speed is ideal for photographers and videographers who are shooting in demanding capture modes, such as high-resolution video and RAW burst photography.
SPEED CLASS (SD & microSD):
Speed Class (Class 2 to 10), UHS Speed Class (U1 or U3) and Video Speed Class (V6 to V90) indicate an SD (or microSD) card’s minimum sustained write speed (e.g. 10MB/s for Class 10 | 30MB/s for U3 | 90MB/s for V90) Cards rated V30 and above are able to handle flawless 4K video recording, while those rated V60 and above are optimized for 6K & 8K video at high frame rates & bitrates, as well as simultaneous multi-file recording (e.g. RAW + JPEG, multiple video streams created by 360º cameras, video + still + GPS data, time-lapses, etc.)
ULTRA DIRECT MEMORY ACCESS & VIDEO PERFORMANCE GUARANTEE (CompactFlash & CFast 2.0):
Ultra Direct Memory Access (UDMA) indicates the maximum bus speed at which a CompactFlash (or CFast 2.0) card can transfer files. UDMA 1 supports speeds up to 16.7MB/s, while UDMA 7 can reach up to 167MB/s (10x faster).
Video Performance Guarantee (VPG) indicates a CompactFlash (or CFast 2.0) card’s minimum sustained write speed (e.g. 20MB/s for VPG-20 | 65MB/s for VPG-65 | 130MB/s for VPG-130) Cards rated VPG-65 and above are able to handle flawless 4K video recording, while those rated VPG-130 (CFast 2.0 only) are optimized for 6K video at high frame rates & bitrates.
X-RATING:
Another way of identifying a memory card’s maximum transfer speed. To determine a memory card’s maximum transfer speed in megabytes per second (MB/s), multiply the X-rating by 150 and divide by 1,000.