UHS-II

Technical Details

UHS-II cards feature 17 contacts compared to 9 in standard SD cards, with the second row of contacts enabling parallel data transfer. The interface operates using Low Voltage Differential Signaling (LVDS) at 1.8V and achieves theoretical maximum speeds of 312 MB/s in full mode. In practice, high-end cards like the SanDisk Extreme Pro V90 deliver write speeds of up to 260 MB/s. UHS-II is backward compatible with UHS-I devices, but will then operate only at UHS-I speeds.

History & Development

The SD Association introduced UHS-II in June 2011, with the first cards appearing in 2014 from manufacturers like SanDisk and Lexar. The standard was developed as a direct response to 4K video recording, which began appearing in consumer cameras from 2012 onwards. In 2017, the V90 video speed class followed, guaranteeing sustained write rates of at least 90 MB/s. Current UHS-II cards also achieve optimized performance for app usage with the Application Performance Class A2.

Practical Use in Filmmaking

UHS-II enables lossless 4K RAW recording in cameras like the Panasonic GH5, which produces data rates of up to 400 Mbit/s. For high frame rate recordings (120fps in 4K), the high write speed prevents buffer overflows and recording interruptions. Documentary filmmakers benefit from longer continuous recording times without card changes. Fast transfer significantly reduces backup times on set: a 128GB card loads in under 8 minutes instead of 25 minutes with UHS-I.

Comparison & Alternatives

While UHS-I is sufficient for Full HD and standard 4K recordings, UHS-II is essential for high-bitrate codecs like ProRes RAW or Cinema DNG. CFexpress Type B offers significantly higher speeds of up to 1,700 MB/s but remains reserved for professional cameras. XQD cards achieve similar transfer rates to UHS-II but are larger and more expensive. For streaming workflows with low bitrates, UHS-I cards are sufficient; for RAW material or HDR recordings, there is no way around UHS-II.