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Sunday, July 1, 2007

Gadget Bag: The State Of Memory Cards


Storing images in your digital camera has never been faster or cheaper. We‚’ll take you through the current selection of cards and options.


The State Of Memory Cards

Digital memory cards just keep getting better and cheaper. Digital SLRs, camcorders and other multimegapixel cameras require memory cards that deliver very large storage capacity and high performance in terms of read and write speed. Noncamera applications and other digital devices—cell phones and PDAs in particular—require storage media that’s very small and thin. The memory-card industry has met and exceeded all of these requirements. Meanwhile, fierce competition among card makers for market share has kept retail prices surprisingly low.

The State Of Memory CardsYou may or may not be able to take advantage of all of the recent advances in memory-card technology, but you can, at least, use the best card that’s compatible with your system. And you can enjoy the bargain pricing.

Physical Aspects

For the most part, memory cards aren’t interchangeable from one type to another. However, adapters that allow the one card type to fit and function in a card slot designed for another card type are becoming commonplace. For example, Sony offers two different Memory Stick adapters, one to fit CF card slots, the other to fit Memory Stick PRO.

Currently, SD (Secure Digital) is the most popular card type.

The State Of Memory CardsSlightly smaller than one frame of 35mm film (24mm x 32mm), SD offers high maximum capacity (2 MB) and outstanding performance characteristics. MultiMediaCards (MMC) are the same physical size and shape and will often work in cameras that were built to use SD. There are some exceptions, however, because the electrical contacts are different. The Mini SD card is much smaller—only 37 percent of the volume of an SD—and can be used in SD applications via an adapter without performance loss.

SDHC (the HC stands for High Capacity) is the latest development in the SD family and was designed to stretch the 2 MB capacity limitation of standard SD all the way to 32 MB. SDHC is not backwards compatible with SD—but you can use standard SD in SDHC host devices. In an attempt to bring some sensibility to speed ratings, all official SDHC cards are marked according to their performance class. For example, Class 2 cards (the slowest) must deliver sustained read and write speed of at least 2 MB per second. Class 4 equates to 4 MB per second. This new speed rating system makes it easier for consumers to select the right card for a particular application. However, all of the confusion hasn’t yet disappeared because some cards are capable of higher burst rates and are promoted as such.

The State Of Memory CardsCompactFlash (CF) has been the traditional favorite for digital SLR cameras because of its large maximum capacity, but lately it’s been losing ground to SD. CompactFlash cards are available in two styles: Type I (the more common) and Type II. The difference is the card’s thickness: Type I cards are 3.3mm thick, Type II cards are 5mm thick. You can use a Type I card in a Type II slot but not the other way around. CF+ is an enhanced version of CF that extends compatibility to wireless communications cards and other Type II devices—including Microdrives. A Microdrive is the same form factor as CF Type II but isn’t really a CF card at all. Instead of using flash memory, Microdrives store image files on a miniature hard drive.

The State Of Memory CardsSony cameras use Memory Stick, Memory Stick PRO or Memory Stick PRO Duo (although the Sony Alpha 100 also accepts CF). The current Memory Stick PRO version offers high capacity (up to 8 GB) but can’t be used in some older Sony cameras.

One more type—the xD-Picture Card—is used only in Olympus and Fuji digital cameras. It’s available in capacities up to 2 GB, with larger sizes expected in the future. There are two types: Type H offers speed advantages but isn’t 100 percent compatible with type M. Check your owner’s manual or the camera manufacturer’s Website before you buy.

The State Of Memory CardsCapacity
Memory card prices are quite reasonable these days. There’s no excuse for not having at least a 2 GB card (higher for a D-SLR). Nonetheless, when you go on vacation, take a spare.

The number of image or movie files that can be stored on a card of a specific capacity varies so much from model to model that it’s impossible to generalize. The total is influenced by many factors, including file format (RAW files are huge), compression ratio (i.e., Fine vs. Standard) and other considerations. Best bet is to buy a card so large that you’re unlikely to fill it during one shooting session.

Speed

As mentioned above, the SDHC speed class ratings are a step toward a standardized way of understanding how cards perform in terms of sustained read and write speed. CompactFlash, on the other hand, as well as standard SD cards, is often categorized by the X factor. The same measurement method is used to rate the throughput of CD and DVD writers and works as follows: 150 KB per second is "1X" and all other speeds are expressed as multiples of that speed. For example, 80X means a write/read speed of 12 MB per second (150 KB x 80 = 12,000 KB or 12 MB). Rule of thumb: high-speed cards can capture images and play them back faster than slower cards can; though slower cards cost less and work great in everyday applications.


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