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While you may have a memory card that fits into your camera, it doesnt
automatically mean that youll 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 were 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, theres 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 youll 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, theyre 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 non-volatileit 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. Its 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 theres 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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