A quick guide to buying the best SD card for a digital camera to shoot movies
As I wrote in a recent post, I'm buying a new digital camera. That means thinking about which SD card is best to get for the camera. Fortunately the memory card format war is largely over, meaning pretty much all digital cameras today use the SD card format, but there are multiple types of SD cards. Primarily they vary on memory card speed and most of the card makers print a speed like "15 MB/second" on the card, like on my two-year-old card, or the one shown here which says 94 MB/second.
According to the manufacturer of this camera, for general use any speed above 6 MB/second will be fine, but for those wishing to take pictures at a high rate, or to shoot movies, they'll want an even faster card. What's going on?
The issue is the rate at which the camera can write pictures to the card. This camera can shoot at 8 frames per second, and the resolution is 16 megapixels. By shooting in both JPG and RAW format this means each picture will require well over 20 megabytes of storage, and at 8 frames a second you're talking 160 megabytes/second of data flowing to the card. My math might be off because I did that off the top of my head, but the point is that at a high picture rate the camera is going to be writing a lot of data to the card.
SDHC and SDXC cards support high capacity (SD High Capacity or SD Extended Capacity), meaning it's SDXC or SDHC that allows the card to hold 64 gigabytes of data or whatever.
What determines the writing speed is the "class" number, e.g. a "class 4" card supports up to 4 MB/sec. A newer designation is UHS-1, or Ultra High Speed, and support rates up to 104 MB/sec.
Numbers like that make me think my math was off earlier, but even if the numbers ended up wrong the idea is correct. Shooting at a high frame rate means lots of data. Ergo, shooting pictures at a high frame rate, or shooting movies, means cards supporting a high data rate. Such as the pictured card from Sony.