The SD Association (SDA) has introduced a Video Speed Class rating, designed to identify cards capable of 8K, 4K, 3D and 360° video capture. The speed class, which guarantees minimum sustained performance, comprises five ratings: V6 (6MB/sec), V10 (10MB/sec), V30 (30MB/sec), V60 (60MB/sec) and V90 (90MB/sec).
Part of the Secure Digital 5.0 standard, the Video Speed Class ratings not only make use of the latest (and future) NAND technologies but are also closely tied to them. As such, a V30 card is only guaranteed to give sustained 30MB/sec performance when paired with a device that can make use of the relevant data transfer methods. In older devices it may give lower performance.
The SD Association’s intention is that device makers will specify the Video Speed Class requirements (and hence compatibility) of their devices so that customers know to buy a card of that rating or higher.
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| It all looks fairly simple until you realize that a V30 card may only operate at Class 10/U1 speeds if the device can’t make use of its transfer behavior. This explains why the SDA hasn’t just expanded the UHS speed class system, but risks adding further confusion if device makers don’t communicate their devices’ requirements much more prominently. |
Another fine mess?
Unhelpfully, the latest speed classes will come in addition to the existing need to consider card type (SDHC or SDXC) and interface standard (UHS-I and UHS-II), and will run in parallel with the two current speed rating systems (Class 1-10 and U1/U3), which have confused consumers up until now. And, no doubt, card makers will complicate matters still further by quoting maximum read and write speeds, which do nothing to tell you whether a card will be fit for purpose (or any faster in real-world use).
To illustrate the current complexity: shooting XAVC S video on the latest Sony cameras requires an SDXC card (which can handle larger individual files), and one that’s rated U3 to capture 4K. So, in this instance, the cards pictured at the top of this story, for all their promises of 240MB/s write speeds, would fail on both counts.
The Video Speed Class rating system doesn’t appear to simplify this system, since an SDHC card still could not record 4K on current Sony cameras, no matter what V rating is printed on it. The new system appears to do a good job of ensuring SD cards are able to make the best use of the next generations of memory technology, but will require widespread cooperation and communication to avoid even more customer confusion.
Products supporting the new Video Speed Class are anticipated to arrive on the market ‘soon.’
Via: SD Association
Articles: Digital Photography Review (dpreview.com)
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