What’s better than a media card with a large storage capacity? How about one with unlimited capacity? Eye-Fi makes SD media cards with built-in Wi-Fi capabilities to wirelessly transfer image and video files across a wireless network. You can upload as you shoot, skipping the tethered download process altogether. The cards have a maximum capacity of 4 GB, so when you shoot out of range of a wireless network, you can still store lots of images until you’re back within range.
With so many media card options, it can be confusing to understand compatibility. Take the HC denominator, for example: Any SD card can work in any SDHC-compatible device, but the reverse isn’t true. (The same goes for mini and micro SD/SDHC formats.) Likewise, just because a CF card is marked UDMA, that doesn’t mean your camera is certain to perform better with the card inside. If you’re using the newest generation of DSLRs to record HD video or shoot large photos at high speed, chances are your camera’s manufacturer has built-in UDMA functionality to make full use of the accelerated data transfer these cards offer.
UDMA, or Ultra Direct Memory Access, represents the newest high-speed transfer protocol in CompactFlash media cards—the shared language two devices use to transfer data. UDMA represents the newest way to transfer data quickly, so cards marked with the identifier are recognizable as high performance—though not all cameras are designed to take full advantage of the cards’ efficiencies.
The ability for a media card to move data quickly is paramount for fast shooting and video recording—particularly as file sizes and video resolutions grow exponentially. Use an outdated, slow or otherwise lagging media card, and you can find yourself waiting to shoot until the card has caught up with its processing and storage duties. This data-transfer rate affects two major aspects of the photo workflow: shooting and downloading, which determine how fast the card can record images in the camera and how fast images are offloaded into the computer.
The data-transfer rate of a media card is measured in megabytes per second, or MB/s. While this number affords a good way to compare one card’s speed to that of another, these numbers also are expressed often as an “x” rating—i.e., 100x or 300x—in much the same way that recordable CD and DVD media are rated. Currently, cards 300x and faster are considered high speed, with maximum ratings of 666x representing a data-transfer rate of 100 MB/s.
Speed class is a broader term used with SD card variants to specify compatibility with various types of image-making activities. Class 2 cards, for example, work fine for basic video recording. Class 4 cards are upgraded to allow HD recording and fast shooting of stills. Class 6 cards offer the current best performance for professional video and stills at the highest available resolutions.
Some photographers choose to prioritize capacity over speed. For others, the reverse is true. Whichever features are more important to you, know that you likely can have any two of the three ideal features—high capacity, fast speed and low price—but not all three in the same media card. The best storage options for high-resolution digital stills and HD video capture, which require not only high capacities but also very fast data-transfer rates, are usually the most expensive.