Flash memory cards--CompactFlash, Secure Digital Card, etc.--are getting faster and faster. Recently, 150x cards can be had for a mere $5 dollars. Few know exactly what 150x really mean. Sure everyone knows that the higher the number, the faster the card. And sure, 150x is three times faster than a 50x card. But exactly how fast can you save an image at 150x?
In reality 1x is equivalent to 0.15 MB/s, or 1.2 Mb/2. (Don't know the difference between MB and Mb? See Megabytes vs. Megabits.) The chart below shows the speed factors and their equivalent transfer rate.
|Transfer Rate (MB/s)
|Transfer Rate (Mb/s)
Just because you can buy a 200x flash memory card today doesn't mean that you can read or write the data at 200x. Whether you can take full advantage of the speed of the card depends on your equipment. If your digital camera's electronics maxes out at 100x, then that's the speed at which it could read and write image files. Similarly, if your memory card reader can only read and write at 50x, then a 200x card will do no more good than a 50x card.
See the next section for methods determine how fast your equipment can read/write data to a card.
What can you do with this conversion knowledge? Well, you can determine how long it will take your digital camera to save a photograph onto a particular card.
For example, a raw image shot with the Panasonic Lumix DMC-LX1 takes up 16.1 MB of space. Using the chart above, you will see that it will take just over 1 second to save this photograph on a 100x card.
You can also do the reverse. If it takes the Panasonic Lumix DMC-LX1 1 second to save a 16.1 MB raw image, then you know the camera is capable of writing the data at 100x.