Picking the right SD card class makes a difference when shooting video.
A number on the side of Secure Digital memory cards gives a key indicator of performance. It's the card's speed-class rating, signified by the numerals two, four, six, or 10. The class shows the card's minimum "write speed," or how fast data will transfer to the card from a digital camera, camcorder or other device. Choose the right class, especially when shooting video, which requires a minimum sustained write speed.
Class 2
A Class 2 card, the lowest-cost option, provides a minimum write speed of at least 2 megabytes per second (MB/s) and is suitable for standard-definition video recording, according to the trade group SD Association.
Class 4
Class 4 cards, with a 4 MB/s rating, are recommended for MPEG-2 HDTV recording.
Class 6
The 6 MB/s minimum performance of Class 6 cards accommodates a professional video camera and consecutive high-megapixel shooting with a digital camera.
Class 10
Class 10 cards offer a minimum write speed of 10 MB/s and support full high-definition video recording and HD still-photo consecutive shooting.
Capacities
Secure Digital cards come in a variety of capacity formats. SD cards range up to 2 gigabytes of storage space. SDHC cards, the most widely used as of 2010, range from 4 to 32 GB. The newest generation, SDXC, will range up to 2 terabytes in capacity, according to the SD Association.
New Speed Ratings
SDXC and SDHC cards that carry a new "Ultra High Speed" rating symbolized by a "1" within a "U," began to emerge in 2010. Cards in this new category will be capable of data transfer of up 104 megabytes per second.
Choose a Class
When you consider which card to use, first consult the manual for your camera or camcorder for compatibility with the various SD capacity formats and a minimum card speed rating. High-definition video, in particular, is demanding and use of a card below the minimum rating sometimes results in dropped frames or other problems. Some manufacturers also tout the maximum write speeds of their cards--especially important when shooting photos in bursts.
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