How Fast Is YOUR Memory Card? There Are Good Reasons To Know
How fast is your memory card? Don't be embarrassed if you have no idea.
The important question is whether or not you know why it's advantageous
to use high-speed cards. What are the benefits and are they worth the extra
During the mid-90s, when consumer-level digital cameras first began to appear, the world of memory cards was very small. There were only a few formats, and maximum capacity was low--very low compared to now. But then again, cameras of that era had modest requirements. It was not uncommon for digital cameras to be delivered to consumers with a 4MB memory card. That's Megabyte, not Gigabyte. And that's hard to believe by today's standards, even though that was only 10 short years ago.
First-generation digital cameras failed to deliver the image quality consumers expected, and many were returned to place of purchase. When performance fails to meet expectations, the perfect storm of dissatisfaction is created. That storm helped fuel the technological innovation that drove performance levels higher and higher. The quality improved and image files grew larger. And of course, memory cards improved at an equal or even faster pace. Those improvements included advancements in read and write speed. Then, as now, memory card development is device driven.
And card development isn't over. Recent announcements of 8- and 10-megapixel mass-market cameras raise the bar yet again. Along with the need for greater capacity memory cards comes the need for faster speeds. Cameras are being built with more on-board memory and larger buffers, which enable them to shoot several shots in rapid sequence. High-speed cards allow the camera to write the data from the buffer fast enough to deliver the camera's published specifications.
The Importance Of Speed
Here is why speed is important: Let's assume for a moment that you have a large back yard, several dead trees, and a wood chipper. It's 200 ft from the front of your yard to the back boundary where the chipper sits. It takes you less than a minute to carry a load of limbs to the chipper but it takes the chipper 2 minutes to mulch each branch. The point is that even if you are able to carry an enormous load of dead wood on each trip, you will be waiting on the back end for your mechanical partner to digest it. On the other hand, if the chipper was able to process the twigs as fast as you can feed it you'll be able to work much faster. It doesn't matter if the chipper is actually faster than you are--as long as it is at least as fast.
Exactly what makes a card high speed? How are cards categorized? Card manufacturers apply the labels themselves, and in some small way that can add to the confusion.
Simply stated, "speed" refers to how fast the card can handle data. Strictly speaking, the specification is expressed as two separate measurements, the sustained sequential write speed and sustained sequential read speed. Fast write speeds are beneficial when capturing images, in particular when working with large image files or long sequences of images. Fast read speeds improve playback, review, and download speeds.
Under ideal conditions, cards that write and read data faster than average allow you to capture images and play them back faster than is possible with a slower card. There are certain variables that can prevent the theoretical specification from being realized in the real world. However, all other things being equal, faster cards will read and write faster.
Most card manufacturers use the same classification system and same terminology that's used to rate the read and write speed of optical drives, CD players, and DVD writers. That is, 150KB per second is "1x" and all other speeds are indicated as multiples of that level. Therefore, 80x means sustained sequential write and read speeds of 12MB per second (150KB x 80 = 12,000KB or 12MB). Conversely, a card rated at 20MB per second would earn a rating of 133x (20MB/150KB = 133).
Some card manufacturers simply state the throughput measurement without doing the mathematical calculation. Panasonic, for example, lists the actual specification. Their latest Pro High Speed Secure Digital cards write and read at 20MB per second. Still others lean toward using a sub-brand label to identify high-speed products. At Kingston Technology we believe that consumers understand and can relate to the "x" standard because they have been exposed to it in the past through CD players and DVD writers. We also brand our high-speed products so that they are easy to identify without a lot of fuss.
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