xD-Picture Card
xD-Picture Card is a type of flash memory card, used mainly in digital cameras. xD originally stood for extreme Digital. The cards were developed by Olympus and Fujifilm, and introduced into the market in July 2002. Toshiba Corporation and Samsung Electronics manufacture the cards for Olympus and Fujifilm. xD cards are now sold under other brands, including Kodak, SanDisk, PNY, and Lexar, but are not branded with the respective companies' logos, except for Kodak.
xD cards are used in Olympus and Fujifilm digital cameras and Olympus digital voice recorders; Fujifilm also made an MP3 player (xD-MP3) that used the cards. As of 2008, xD cards are available in capacities of 16 MB (16 MiB), 32 MB, 64 MB, 128 MB, 256 MB, 512 MB, 1 GB (1 GiB) and 2 GB.
The original xD cards were available in 16 MB to 512 MB capacities. The Type M card, released in February 2005, uses Multi Level Cell (MLC) architecture to achieve a theoretical storage capacity of up to 8 GB. As of August 2006, Type M cards are available in sizes from 256 MB to 2 GB. However, the Type M suffers slower read-write speeds than the original cards.
xD-Picture Card, 512M, type H
The Type H card, first released in November 2005, offers higher data rates than Type M cards (theoretically as much as 3 times faster). As of 2008, Type H cards were only available in 256 MB, 512 MB, 1 GB, and 2 GB capacities. Both Fuji and Olympus discontinued the production of Type H cards in 2008, citing high production costs.
The Type M+ card, first released in April 2008, offers data rates "1.5 times" that of Type M cards. As of 2008, cards are available only in 1 and 2 GB capacities.
Olympus says that its xD cards support special "picture effects" when used in some Olympus cameras, though these software features are not intrinsically hardware-dependent. Type H and M+ cards however, are required in newer models to capture video at high rate (640×480×30). Due to changes in the cards' storage architecture, newer Type M and H cards may suffer compatibility issues with some older cameras (especially video recording). Compatibility lists are available for Olympus: Olympus America’s and Fujifilm’s. The newer cards are also incompatible with some card readers.
Pictures may be transferred from a digital camera's xD card to a personal computer by plugging the camera into the PC (via a USB cable), or by removing the card from the camera and inserting it into a card reader. In both cases, the computer sees the card as a mass storage device containing image files, although software or firmware can alter this representation. Card readers may be integrated into the PC or attached via cable. Adapters are available to allow an xD picture card to be plugged into other readers (and in some cases cameras), including PC card, parallel port, CompactFlash and SmartMedia.
As of 2008, the xD format primarily competes with Secure Digital card (SD), CompactFlash (CF), and Sony's Memory Stick.
Advantages
- xD cards are fast in comparison with older formats such as SmartMedia (SM), MultiMediaCard (MMC), and Memory Stick (MS).
- xD cards have a small form-factor in comparison with other formats (although both microSD and M2 are significantly smaller).
Disadvantages
- Small maximum capacity relative to other memory card formats. First-generation xD cards have a maximum capacity of only 512 MB; while Type M expands the theoretical maximum capacity to 8 GB, as of January 2009 there are no cards available with capacity greater than 2 GB.
- Although physically smaller than Secure Digital and Memory Stick cards, xD cards are larger than these competitors' reduced-size variants (microSD, and Memory Stick Micro).
- xD cards are generally more expensive than other memory card types.
- xD cards are less widely supported by camera, card reader, and accessory manufacturers than other formats.
- The xD card format is proprietary to Fujifilm and Olympus, just as the Memory Stick format is to Sony. This means that no public documentation or implementation is available (see below for reverse-engineering results). By comparison, the MultiMediaCard and CompactFlash formats are described by completely open and free specifications, and a partial specification for the SD format is freely available.