How to select a memory card for your camera

     Print Edition: July 2012

After the camera and lens, the memory card is now the most important piece of equipment in your photography toolkit. When selecting a memory card, you should know the difference between popular card formats, determine how much storage you need, and understand the role card speed plays when capturing photos and videos. Susan Park, Director, Retail Product Marketing, SanDisk, explains:

FORMAT: The vast majority of digital cameras use either Secure Digital (SD) cards or CompactFlash cards. CompactFlash cards often deliver the fastest performance and largest storage capacities. The SD format offers performance and capacity levels for everyone from beginners to elite pros. SD-compatible cameras can support one or all of capacity types which determine the type of card you must use. SD supports up to 2 GB, SDHC 2GB to 32GB and SDXC 32GB to 2TB.

CAPACITY: Capacity refers to the amount of digital content a card can store, and is measured in gigabytes. So while deciding how much capacity to purchase, consider how often you will shoot, how long each shooting session will last, what file sizes your camera will produce and whether you will be shooting video. An 8 MP JPG might consume only two megabytes (MB) of storage, but a high-resolution RAW image can reach 24MB or more; and just 10 minutes of Full HD 1080p MPEG-4 video can consume up to 4 GB of space. Casual compact camera users can get by with an 8GB card, but DSLR users should opt for at least a 16GB version.

Speed determines how many images you can capture during a shooting sequence, what quality of video you can record and how quickly you can transfer your images to a computer. A card's speed measures the maximum sequential speed at which you can perform certain functions. "Write" speed indicates how quickly you can write data to the memory card. "Read" speed indicates how quickly you can transfer data from the memory card to a host device. Cards that write faster minimise lag time between shots. The faster a card's write speed, the less time you will spend waiting for it to process each image, which means capturing more pictures in a given timeframe. This is especially important when using burst mode to shoot images that require precise timing such as a batter hitting a baseball, a bird in flight or a racecar crossing the finish line. Read speed measures how quickly a card can transfer data to another device. A card that reads at 45 MB/sec can take five minutes to transfer 12 GB of files, while a card that reads at 95MB/sec can transfer those same files in roughly half the time. X SPEED: Some manufacturers measure card performance using the "X" speed, similar to the common CD-ROM performance measurement of X = 150KB/sec. The speed reference may vary depending on the manufacturer. Write speed is the most important criterion when capturing photos.

Unlike photos, which flood the memory card with lots of data in a single instant, videos create a sustained stream of data. Large image files need fast write speeds, while videos require a minimum sustained write speed for recording. A memory card's ability to record video is measured by its video-capture rating, which appears in various ways depending on the card format. CompactFlash cards sometimes display a video performance guarantee (VPG), which indicates that the card can perform a minimum sustained write speed of 20MB/sec for video recording. SD cards often display a "class" rating, which measures the minimum sustained write speed required for uninterrupted video recording. A card's class rating indicates its minimum guaranteed data-transfer rate, measured in MB/sec. Class 4 cards deliver a minimum sustained write speed of 4MB/sec, for Class 10 cards this is 10MB/sec. Newer SD cards, particularly high-performance cards based on the Ultra High Speed (UHS) bus interface, display a new video-recording measurement called U1 (UHS Speed Class 1). This speed class indicates that the card is capable of producing a minimum sustained write speed of 10MB/sec.

MATCHING: When selecting a memory card, follow this rule: match the card to your camera's features. If your camera can record Full HD videos, make sure your card can too. If your camera can shoot in burst mode, make sure your card's write speed is fast enough to handle the flood of images.

Courtesy:Gadgets and Gizmos

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