Ultra High Speed spec for SD guarantees HD video
updated 12:05 pm EDT, Thu June 24, 2010
UHS spec promises ultra-fast transfers
The SD Association today defined a new specification for very fast SDHC and SDXC cards. Ultra High Speed I (UHS-I) will guarantee a maximum interface speed of 104MB per second, or four times the 25MB speed of regular cards. As long as they're used with cameras, readers or other devices that can recognize the speeds, UHS cards should have no trouble recording HD video or shooting continuous RAW photos.
It wasn't mentioned when UHS-I cards would reach the market, but the Association considers the labeling a green light for cards based on the faster technology to reach the market. Using the full speed will also require host devices that are still currently rare, as even SDXC readers won't necessarily address the faster speed.
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Confusing!
This is just piling onto the already confusing numbers.
Currently, we have SD(HC/XC) cards at Class 2, 4, 6 and 10. These numbers indicate the minimum guaranteed write speed of 2, 4, 6 and 10 Megabytes per second.
So, while the highest class was 10MBps, the fastest data transfer until today was 25MBps, and they bumped this up to 105MBps. Should we now expect something like Class 40?
On a related subject, it doesn't help the confusion that camcorder makers express their video encoding rates in Mbps (Megabits per second), rather than MBps (Begabytes). So, since there are 8 bits in a byte, Class 2 ends up being 16Mbps; Class 6 is 42Mbps, etc.
If only there were one single, common way to express these values, people wouldn't needlessly be buying Class 10 cards, so that they can shoot AVCHD at 8Mbps (Class 10 is 80Mbps).