东汉皇帝和皇后列表:数码相机常用储存卡有几种？价格、性能、区别何在？

Storage Card
By Vincent Bockaert

Storage cards are to digital cameras what films are to conventional cameras. They are removable devices which hold the images taken with the camera. Storage cards are keeping up with the rapidly changing digital camera market and are trending in the following direction:

larger capacities (several GB) and faster write speeds to accommodate higher resolution images and shooting in RAW
lower prices per MB or GB of storage
smaller form factors for smaller digital cameras

The only downside of all this good news is a proliferation of storage card formats, making it more difficult to use cards across different cameras, card readers, and other devices (such as PDAs, MP3 players, etc). The image and table below give you an idea of how the sizes of typical formats compare:

Card Type Dimensions in mm Volume in mm³
CompactFlash II / Microdrive 42.8 x 36.4 x 5.0 7,790
CompactFlash I 42.8 x 36.4 x 3.3 5,141
Memory Stick 50.0 x 21.5 x 2.8 3,010
Secure Digital 32.0 x 24.0 x 2.1 1,613
SmartMedia 45.0 x 37.0 x 0.8 1.332
MultiMediaCard 32.0 x 24.0 x 1.4 1,075
Memory Stick Duo 31.0 x 20.0 x 1.6 992
xD Picture Card 25.0 x 20.0 x 1.7 850
Reduced Size MultiMediaCard 18.0 x 24.0 x 1.4 605

CompactFlash
CompactFlash is a proven and reliable format compatible with many devices and generally ahead of other formats in terms of storage capacity. Capacities above 2.2 GB require that your camera supports "FAT32". CompactFlash comes in Type I and II which only differ in thickness (3.3mm and 5.0mm) with Type I being the most popular for flash memory, while Type II is used by microdrives.

Microdrives
Pioneered by IBM, microdrives are minute hard disks that come in CompactFlash Type II format and typically offer larger storage capacities at a cheaper cost per megabyte. However, CompactFlash has been catching up with higher capacity cards. Microdrives use more battery power, create more heat (which can result in more noise) and have a higher risk of failure because they contain moving parts.
SmartMedia
Bigger in surface than CompactFlash but much thinner, they are more fragile and known to be less reliable. This format is gradually being phased out of the market with virtually no new cameras being announced supporting this format.
Sony Memory Stick
Yet another standard, set by Sony but now also manufactured by others such as Lexar Media. The main drawback is that there are fewer cameras using this type of memory, although their number is gradually increasing. So if you buy another brand of camera later on, you may not be able to use your memory sticks. Memory sticks are more expensive per megabyte because there is less competition in the market. Although their capacity continues to increase, they tend to lag behind CompactFlash in terms of maximum capacity. Several variants exist such as Sony Memory Stick with Select Function, Sony Memory Stick Pro, Sony Memory Stick Duo, and Sony MagicGate.
Secure Digital (SD)
Supported by the SD Card Association (SDA), this compact type of memory card allows for fast data transfer and has built-in security functions to facilitate the secure exchange of content and includes copyright (music) protection which makes them more expensive than the similar MultiMediaCards which we will discuss next. SD cards have a small write-protection switch on the side, similar to what floppy disks have.

MultiMediaCard/SecureMultiMediaCard/Reduced Size MultiMediaCard (MMC/SecureMMC/RS-MMC)
Supported by the MultiMediaCard Association (MMCA), MultiMediaCards have the same surface but are 0.7mm thinner than SD cards and have two pins less. Hardware-wise MMC cards fit in SD card slots and many, but not all, SD devices and cameras will accept MMC cards as well. Check out the specs before you buy. Two variants are SecureMMC, similar to SD, and Reduced Size MMC.
xD Picture Card
Another format aimed at very small digital cameras, developed by Olympus, Fujifilm, and Toshiba.

Other Formats
Older formats include floppy disks and PCMCIA cards. A few models support writing on to 3-inch CD-R/RW discs. Some low-end cameras don't have removable storage cards but instead have built-in flash RAM memory.