CompactFlash cards offer rugged, high-capacity storage. Favorites of professional photographers and consumers alike, CF cards come in a variety of sizes and write speeds. Both of these factors influence price, but you also have to decide between Type I and Type II versions, which are different thicknesses. Don't confuse them with the competing standard, the smaller-format SD; they aren't interchangeable. Once you understand the key differences in capabilities and price, choosing the right CF card should not be an arduous task.
1General Overview: CompactFlash media come in varying speeds, ranging from standard CompactFlash, CF+, 3.0 and 4.0. CompactFlash as of 2012 is based on Negated And or Not anD -- or NAND -- technology, a form of flash memory. This memory type is non-volatile, meaning it does not use an internal battery to assist with data storage. Type I and II compact flash media are 3.3 and 5 millimeters thick, respectively. Generally, conventional flash-based CF media are the Type I variety, while magnetic drives like CF MicroDrive are Type II. The latter type is compatible with PCMCIA slots in laptops and desktop computers using the correct adapter to increase storage capacity for the device.
2Speeds: Conventional data storage read and write speeds are not normally a large factor when selecting media, although there are exceptions to this. Photographers need to snap pictures at speeds equal or better than conventional film-camera speeds. Digital single-lens reflex or DSLR cameras are the choice of professional photographers, necessitating fast CF write speeds. CompactFlash offers up to 133x for extremely fast shooting, writing at 66 megabits per second for Revision 3 cards. Slower speeds are fine for better point-and-shoot consumer-level cameras that often do not require the blazing response times offered by more expensive faster media. Even faster media offered by SanDisk and other manufacturers offer speeds up to 100mb/s at capacities up to 128 gigabytes for your HD camcorder or pro-grade DSLR shooting RAW images.
3Durability Considerations: Most flash memory media tends to be durable. CompactFlash cards are rated to survive falls from 10 feet or less, but anecdotal stories involving tens of feet or even prolonged exposure to water outside of a camera with 100 percent data integrity are prevalent. MicroDrive media involve magnetic read and write cycles, similar to a tiny hard drive. Because these devices involve moving parts, durability may be more of a concern in rugged conditions. As with any electronic device, care should always be taken when handling and storing CompactFlash media to ensure precious media and photos are not at risk.
4Other Functions: Other devices may be housed in CompactFlash shells, including USB ports, wireless modems and Bluetooth modules. Known as CF+I/O, these devices act as adapters, using the 50-pin CF card format as a medium of transferring data in the form of a small PCMCIA card. These devices do not read and write data from an external source like a standard CompactFlash card, so you need to pay attention to labeling on the package.