[Flash Card Basic] What do the various Speed Classes mean (C, U, V ratings)?

Speed classes are crucial for understanding a card's minimum sustained write performance, especially important for recording video or continuous burst photography.

• Speed Class (C): The original speed rating, denoted by a number inside a circle.
  • C2: Minimum 2MB/s write speed
  • C4: Minimum 4MB/s write speed
  • C6: Minimum 6MB/s write speed
  • C10: Minimum 10MB/s write speed (common for Full HD video)
• UHS Speed Class (U): Ultra High Speed. Denoted by a number inside a "U" symbol. Requires UHS-compatible devices.
  • U1: Minimum 10MB/s write speed (similar to C10, good for Full HD video)
  • U3: Minimum 30MB/s write speed (essential for 4K video recording, continuous burst RAW photography)
• Video Speed Class (V): Designed specifically for high-resolution video recording, including 4K, 8K, and 360-degree video. Denoted by a "V" followed by a number.
  • V6: Minimum 6MB/s write speed
  • V10: Minimum 10MB/s write speed (Full HD)
  • V30: Minimum 30MB/s write speed (4K video)
  • V60: Minimum 60MB/s write speed (High-bitrate 4K, 8K)
  • V90: Minimum 90MB/s write speed (Highest-bitrate 4K, 8K, professional slow-motion)
• Application Performance Class (A): Introduced for devices that run Android apps directly from the card. Guarantees minimum random read/write IOPS (Input/Output Operations Per Second) and sequential performance.
  • A1: Minimum 1500 IOPS random read, 500 IOPS random write, 10MB/s sequential write.
  • A2: Minimum 4000 IOPS random read, 2000 IOPS random write, 10MB/s sequential write.

How to Read the Labels: A card might be labeled with multiple speed classes, for example, "C10 U3 V30 A1." This means it meets all those minimum specifications.