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
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.
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.)
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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