With old-school film cameras, shutter speed and film speed determined how quickly a photographer could shoot. In modern cameras, it’s the speed of the image-capture circuitry — the “graphic engine” or “imaging engine” — and the memory card used to capture the images that determines how fast you can shoot. The highest-speed SD cards, such as SanDisk’s Extreme and Extreme Pro Series, support exceptionally fast data transfer rates. However, not all cameras are designed to take advantage of them.
Digital Camera Basics
When light comes through the lens of a digital camera, it focuses on an electronic sensor called a charge-coupled device, or CCD. The large CCDs found in high-end cameras can record images ranging from 14 to 20 or more megapixels, while low-end point-and-shoot cameras or cell phone cameras might only create images of 1.5 or 2 megapixels. Images with large numbers of pixels are sharp, detailed and have fully saturated colors, but they also require a lot of processing power. To shoot high definition video or a quick burst of high-resolution images, your camera must support high-speed memory cards.
To minimize confusion for purchasers, the consortium in charge of the SD specification decided to group the cards in classes. For example, a Class 4 card will support full-motion video, but not high-definition video. A Class 10 card enables photographers to shoot full-motion video in HD, or take very high-resolution still photos in rapid succession. The newer Ultra High Speed specification, for high-capacity SDXC cards, restarts the numbering system with UHS-1. The architecture of these cards is different, supporting larger sizes and higher memory speeds both now and in the future. The SanDisk Extreme and Extreme Pro support the Class 10 standard, but take advantage of UHS-1 when they’re used in compatible cameras.
Class 10 Cameras
The majority of high-end professional and consumer cameras support Class 10 SD cards, in either the SDHC or SDXC formats. SanDisk’s Extreme series are SDHC cards, with capacities of up to 32GB. The Extreme Pro series are SDXC cards, with capacities of up to 128GB in 2012 and potential capacities of up to 2TB — 2,000GB — in the future. At Class 10 performance levels, the cards are capable of data transfer rates of up to 30MB per second. Few cameras will take full advantage of these speeds, but any Class 10-compatible camera will perform at the maximum speed supported by its imaging circuitry.
In 2012, only a handful of high-end cameras support the higher speeds of the UHS-1 architecture. Cards such as the SanDisk Extreme Pro are capable of data transfer rates reaching 95MB/second, adequate for the most demanding high-speed, high-quality photography and videography. The UHS architecture will eventually be capable of transfer rates exceeding 300MB/second. High-end cameras such as Nikon’s D7000 or D600 have very fast processors and can take full advantage of current-generation UHS-1 cards such as the Extreme Pro. To learn whether your camera is compatible with UHS cards, consult the manufacturer’s documentation or use the compatibility guide on SanDisk’s website.