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Tuesday, November 6, 2012

Gadget Bag: High-Speed CompactFlash Cards

To take advantage of the latest high-res video HDSLRs, you’ll feel the need for speed and capacity, and contrary to what you may have heard, the death of CF has been greatly overstated

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This Article Features Photo Zoom

Readers of Outdoor Photographer are attracted to DSLRs with large, high-res sensors. We want to record details, shoot wildlife action at high speed and have the ability to crop and enlarge the images to make big prints. Today, we have 36-megapixel DSLRs, and DSLRs and SLTs that can shoot 16- to 24-megapixel RAW files at 12 fps. So the need for fast, high-capacity memory cards has never been greater. And the interest in time-lapse shooting as well as full HD video also requires fast, high-capacity cards. Fortunately, they're available—and for much less money per MB than a decade ago.

You say you shoot landscapes, so you don't need to shoot RAW files at 12 fps? Well, you probably shoot a high-megapixel camera to get maximum detail. Those big RAW files require fast, high-capacity memory cards, and many landscape photographers do HDR images or stitched panoramas, or bracket exposures. These require making a number of shots, preferably quickly so the light doesn't change partway through the sequence. Here, again, a quick memory card is a boon.

Digital cameras have buffers, memory where image files are stored while they're being written to the memory card. Higher-end cameras have bigger buffers and, thus, can shoot more images in a burst before filling the buffer. Once the buffer is full, you have to wait until files are written to the card before you can continue shooting.

Fast memory cards (assuming your camera can take advantage of that speed; most newer ones can) mean writing images to the card goes faster, and you can shoot more quickly. Faster cards (again, assuming your card reader and computer can handle the speed) also mean the images transfer to your computer more quickly.

The most common memory cards for cameras are CompactFlash and Secure Digital (SD). Currently, the fastest CompactFlash cards are somewhat faster than the fastest SDHC and SDXC cards. (XQD cards are faster still, but so far only the Nikon D4 DSLR uses them; the D4 also uses CompactFlash cards.)

CompactFlash Background
At 43x46mm, CompactFlash cards are somewhat larger than other formats like SD. But that also means they're not so easy to lose in the field. There are two types: I (3.3mm thick) and II (5mm thick). All cameras that accept CompactFlash can use Type I cards, but not all can use the thicker Type II. But the newer, faster, higher-capacity cards are all Type I, so that's not a problem. Current CF cards are available in capacities from 2 GB to 256 GB, with speeds of up to 1000X (150 MB/s read, 80 MB/s write). Things to look for are "UDMA 7" and "VPG-20." UDMA stands for Ultra Direct Memory Access, and using UDMA 7 CF cards in UDMA 7-compliant cameras results in the fastest transfer rates—up to 167 MB/s versus 133 MB/s for the earlier UDMA 6. VGA stands for Video Performance Guidance, and VPG-20 means the card can support sustained speeds of up to 20 MB/s for smooth 1080 video with no dropped frames, even with under- or overcranking (high-speed and slow-motion video).


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