Memory card speed is the card's performance with regard to how quickly data can be transferred to or from it. compare cards by the “X” speed, such as 80X, 150X,The card speed is often stated in -Times- ratings i.e. 12X, 40X etc (just as the speed of recordable CD's and DVD's is measured), and sometimes more specifically in megabytes per second (Mb/s).X is the baseline equal to a card accepting 150KB in one second. By today's measure, sub 20X represents a standard speed, 20X to 40X is mid-high speed and over 40X is high speed. The chart below shows the relationship between the two figures.
- 1X = 150KB per second
- 8X = 1.2 Mb/sec
- 10X = 1.5MB per second
- 12X = 1.8 Mb/sec
- 20X = 3.0 Mb/sec
- 25X = 3.8 Mb/sec
- 30X = 4.5 Mb/sec
- 40X = 6.0 Mb/sec
- 50X = 7.5MB per second
- 60X = 9.0 Mb/sec
- 66X = 10.0 Mb/sec
- 80X = 12.0 Mb/sec
- 90X = 15.0 Mb/sec
- 133X = 20.0 Mb/sec
- 150X = 22.5MB per second
- 300X = 45MB per second
Faster cards can accept more megabytes of information per second. But just how much of an advantage is a faster card? With some cameras, there isn’t much advantage to using a faster card, while others will benefit from the high speed.
The Secure Digital Association (SDA) defines three speed classes in order to let users identify speed and performance capabilities of SDHC cards and the host products. The speed class rating specifies a MINIMUM sustained write speed for SDHC cards.
- Class 2 = 2MB per second
- Class 4 = 4MB per second
- Class 6 = 6MB per second
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