Information on SD Cards
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Below is useful information about SD cards and Consumption Rates:

 

 

SD Speed Class Rating (*)

The SD Association defines standard speed classes indicating minimum performance to record video. Both read and write speeds must exceed the specified value. These are defined in terms of suitability for different applications:

  • Class 2 for SD video recording
  • Class 4 and 6 for HD ~ Full HD video recording,
  • Class 10 for Full HD video recording and HD still consecutive recording
  • UHS Speed Class 1 for real-time broadcasts and large-size HD videos

The specification defines these classes in terms of performance curves which translate into the following minimum performance levels, for both read and write, on an empty card:[40]

Class Minimum performance
Class 2 2 M/sec
Class 4 4 MB/sec
Class 6 6 MB/sec
Class 10 10 MB/sec

Speed Classes 2, 4, and 6 assert that the card supports the respective number of MB/sec as a minimum sustained write speed for a card in a fragmented state. Class 10 asserts that the card supports 10 MB/s as a minimum non-fragmented sequential write speed. By comparison, the older "×" rating measured maximum speed under ideal conditions, and was vague as to whether this was read speed or write speed.

The host device can read a card's speed class, unlike the earlier "×" speed ratings. A device can warn the user if the card reports a speed class that falls below an application's minimum need.

 

* - SD card speed information courtesy of Wikipedia