High-capacity memory cards (64 GB–2 TB) for 4K video recording, achieving up to 624 MB/s transfer speeds via UHS-III.
Technical Details
SDXC cards use the same physical dimensions as SD and SDHC (32 × 24 × 2.1 mm) but differ in expanded capacities and speed classes. UHS-I theoretically reaches 104 MB/s, UHS-II with additional contacts 312 MB/s, and UHS-III up to 624 MB/s. Video Speed Classes define minimum write rates: V30 (30 MB/s), V60 (60 MB/s), and V90 (90 MB/s). The cards operate at 2.7-3.6 V and use NAND flash memory technology with wear-leveling algorithms.
History & Development
The SD Association introduced SDXC in January 2009 after SDHC reached its limits at 32 GB. SanDisk launched the first 64 GB cards in 2010. UHS-I followed in 2011, UHS-II with a dual row of contacts in 2011, and UHS-III in 2017. Lexar achieved a read speed of 300 MB/s for the first time in 2017 with the Professional 2000x. Sony and other manufacturers established Video Speed Classes for professional video applications starting in 2012.
Practical Use in Filmmaking
SDXC cards store 4K footage in cameras like the Canon EOS R5 (V90 cards for 8K RAW), Sony α7S III, or Panasonic GH5. For 4K recordings at 400 Mbps, productions require V60 cards; for internal RAW recordings, V90 specifications are needed. Documentary filmmakers appreciate the compactness: a 512 GB card holds approximately 2.5 hours of ProRes 422 HQ in 4K. Backup workflows involve copying footage in parallel to multiple cards or external recorders like the Atomos Ninja V.
Comparison & Alternatives
CFexpress Type B offers higher speeds (1,700 MB/s) for cinema cameras like the ARRI Alexa Mini LF but costs three times as much. XQD cards achieve similar rates but are being superseded by CFexpress. SDXC remains the standard for mirrorless cameras and compact devices, while professional productions opt for CFexpress or SSD recorders for high data rates. MicroSDXC variants are used in action cameras and drones.