XD-Picture Card

The title of this article is incorrect because of technical limitations. The correct title is xD-Picture Card.

xD-Picture Card compared in size with a US 1 cent coin

The xD-Picture Card is a flash memory memory card format developed and introduced to the market in July 2002 by Olympus and Fujifilm, and manufactured by the Toshiba Corporation. (Kodak, SanDisk, and Lexar now also sell xD cards.) xD cards are used exclusively in Olympus and Fujifilm digital cameras, and are available in a range of sizes, from 16 MB to 512 MB. They primarily compete with formats such as Secure Digital Card (SD), Compact Flash (CF), and Sony Memory Sticks. xD stands for "extreme digital."

Typically, an xD card is used as storage media for a digital camera, in a form that can easily be removed for access by a PC. A digital camera would use an xD card for storing image files. With an xD reader (typically a small box that connects via USB or some other serial connection), a user could copy the pictures taken with the digital camera off to his or her computer. Modern computers, both laptops and desktops, rarely have built-in xD slots even when other formats are supported, due to the general lack of popularity xD suffers from. However, PCMCIA and CF adapters are available for xD-Picture cards, enabling them to be used in readers and cameras which do not have native support for the xD format.

The xD card offers a single advantage over its direct competitors: size. An xD card is 20 by 25 by 1.78 mm and weighs about 2.8 g, making it significantly smaller than the matchbook-sized CF card and about half the size of the more-common SD card. As far as size goes, it is much closer to miniSD or RS-MMC, both which are generally used in cell phones rather than digital cameras.

The manufacturer's claimed write speeds for xD-Picture Cards are: for the 16 MB and 32 MB card, 1.3 MB/s. The 64 MB and higher cards achieve 3 MB/s. Both offer a read speed of 5 MB/s. For comparison, Compact Flash memory uses a 150 kB/s baseline, and so a 64 MB xD-Picture Card is equivalent to a 20x Compact Flash card; the current limit of CF is 80x, though 40x tends to be marketed to the professional and serious amateur user.

xD cards offer quite a few disadvantages, however, in comparison to their more-popular competitors.

The most significant disadvantage for a consumer is going to be their limited availability and support. xD cards are only used in Olympus and Fuji cameras. xD card readers are slightly more difficult to find, as well. This means that, unlike SD or CF, someone with multiple devices that use memory cards is going to be unable to reuse xD cards in any of their other devices.

another significant disadvantage is their greater cost, due to the restrictive (and expensive) licensing required to manufacture them. In general, an xD card costs approximately twice as much per-megabyte as an SD card, and about two-and-a-half to three times as much per-megabyte as a CF card.

This problem is exacerbated by the lower maximum capacity of xD cards; as of April 2005, xD cards are only available in sizes up to 512 megabytes (with one gigabyte capacity cards promised by the end of the year), whereas all of the competing formats are available in multi-gigabyte capacities. xD has a lower theoretical capacity, as well; without a format change, xD cards only scale up to 8 gigabytes, whereas the competition has limits ranging from 128 gigabytes (in the case of SD) to two terabytes (in the case of the Memory Stick.)

xD cards offer disadvantages for manufacturers and programmers, as well. Besides the limited need for the cards, given the relatively small number of devices that use them, the specification for xD cards (and thus the information needed to implement their use) is tightly controlled by Olympus and Fujifilm, meaning that anyone wanting to manufacture xD cards, add an xD slot to their device, or write drivers for xD card readers is going to need to both follow whatever rules Olympus and Fuji set and pay whatever price Olympus and Fuji demand. (Some newer Olympus digital cameras even disable panoramic mode when not used with an Olympus-branded xD card.)

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Categories: Solid-state computer storage media