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Thursday, January 18, 2007

Toolbox: Navigating Memory

Get the most from your storage media and digital camera

Toolbox Navigating Memory
While you may have a memory card that fits into your camera, it doesn't automatically mean that you'll get the best performance from either the card or the camera. A 1 GB CompactFlash card may promise storage for hundreds of JPEG images, but when that same card relegates the camera to performing sluggishly, we may well feel that we're more decked out for sweeping off the porch than dancing at the ball.

Along with a variety of memory card formats, including CompactFlash, SecureDigital, xD and Memory Sticks, there's an assortment of features to consider, such as storage capacity, speed, reliability and price. The format issue is easily resolved since your camera determines which type of media card you'll use. Other features have to be considered carefully, however, reducing the convenience of simply pulling a memory card straight off the rack.

Flash Memory
Although there are different formats of storage cards, they're all designed around flash memory chips. Flash memory is a type of EEPROM (electrically erasable programmable read-only memory) that allows data to be written and erased during a single operation. Sometimes compared to RAM found in a computer, flash memory is nonvolatile—it retains data without requiring a constant power supply.

A memory card consists of several flash memory chips and a controller, the latter of which is the on-board software that manages the writing and erasing of data. It's the combination of the flash memory and the controller that impacts not only the speed by which images are recorded to the card, but also how fast that data is transferred from the card to the computer.

Card manufacturers offer data transfer speeds for their products in terms of MBps (megabytes per second), or as 20x, 60x or 133x, but the caveat is that there's no industry standard for measuring performance. Each manufacturer utilizes its own system for evaluating its products. You can have two makes of CF cards, each rated at 40x, but they may deliver slightly different data transfer rates. Despite the difference, this data provides a good starting point for choosing memory.


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