In the market for a memory card? Making the right choice doesn’t have to be complicated. Here’s everything you need to know to be a savvy shopper.

Secure Digital, or SD, is the most popular type. Despite its small size it offers high maximum capacity and outstanding performance characteristics. Multi Media Cards, better known as MMC, are the same physical dimensions and can be used in place of SD in many cameras; however, the electronic interface is slightly different, so MMC will not work in certain other devices. The Mini SD format is smaller than SD and is not widely used in digital cameras but converts to the full sized SD form factor when used with an adapter.

Compact Flash, or CF, provides the highest maximum capacity and is therefore the card of choice for digital SLR cameras and other models that produce large image files. CF cards are available in two variations: Type I and Type II. Type I cards are 3.3mm thick whereas Type II cards are a bit thicker (5mm). Most consumer-level digital cameras are Type I. It’s generally possible to use a Type I card in a Type II slot but not vice versa. It’s also possible to use SD cards in CF appliances by means of an adapter. Another option that matches the CF (Type II) form factor is the Microdrive. Microdrives use spinning media (tiny hard drives) instead of Flash memory to store data and are therefore a bit more sensitive to impact.

Memory Stick and its cousins Memory Stick PRO and Memory Stick Duo are most commonly found in Sony products (there are exceptions). Its elongated rectangular shape resembles a shrunken stick of gum. The current Pro version offers high capacity but cannot be used in some older Sony cameras, so be careful if you own a Cyber Shot S85 or another model of that vintage: you must use the original Memory Stick product. Memory Stick Duo is also used in some phones and in the Sony PlayStation Portable (PSP).

xD Picture Cards are physically the smallest of all popular types. Newer Fuji and Olympus cameras use xD cards and a few accept both xD and Compact Flash. Older models of these brands used SmartMedia, so check your owners manual.

Compact Flash                 8Gb
Memory Stick                  4Gb
Secure Digital                   2Gb
xD                                   1Gb
SmartMedia                128Mb

Unless you’re on a tight budget you should stick with cards 512Mb or larger. The delight of digital lies in the ability to shoot zillions of images and delete the duds. Big cards allow you to keep shooting. If you own a digital SLR or high-end zoom camera, you need 1Gb cards. If you shoot RAW format, 2Gb is a better choice.

Lexar Media rates their cards using the same terminology that’s used to rate the throughput of CD and DVD writers: 150Kb per second is “1X” and all other speeds are expressed as multiples of that standard. Therefore, 40X means a write/read speed of 6Mb/sec (150Kb X 40 = 6,000Kb or 6Mb).

Panasonic simply lists the actual specification. For example, their latest Pro High Speed SD cards write and read at 20Mb per second.  SanDisk offers cards at three performance levels. The Extreme III line writes and reads at 20Mb/sec. The Ultra II and Extreme models have write speeds of 9Mb/sec and read speeds of 10Mb/sec. Their standard line is a little slower.

Both SanDisk and Lexar offer a selection of budget-priced, low capacity memory cards that are marketed toward folks who prefer to use media more-or-less in the same way they formerly used film, that is, storing the images on the card and never deleting them. SanDisk calls theirs Shoot and Save. Lexar Media markets theirs as Digital Film under the Kodak brand. Whether or not you subscribe to the notion of not reusing reusable cards is up to you, but one thing is certain: the cards have very attractive prices, and it’s nice to keep a few around as back up.

No matter what memory card you use, there are two accessories you should not be without. The first is a card case. Cards are small and easy to lose. Cases offer protection and are easier to locate in the bottom of a gadget bag.

But the most useful memory card accessory you’ll ever encounter is a card reader/writer. Adding one to your system is certain to improve your workflow because it eliminates the need to connect your digital camera to your computer to download images. Instead, the card reader connects via high speed USB (2.0) and offers up to a dozen interfaces to accommodate all available card formats. When the card is inserted into the reader it is recognized as a mass storage device and the images are immediately available. The SanDisk 12-in-1 card reader, which sells for around $30, is a typical example, but there are many brands and styles on the market, including the Multi Card Reader from Lexar Media.