When buying an SD card for your camera you should consider the speed class of the card to ensure your are getting the right performance for the intended usage of the card. I learned this lesson recently with a digital compact that limited HD video recording to thirty seconds clips because the speed class of the storage card was too low and couldn’t keep up.

When reading the documentation for my particular compact digital camera it states the speed class of the memory card should be speed class 4 to ensure video recording performance.

There are currently three speed classes, which indicate the minimum data transfer speed, of SD cards:

• Class 2 offering a guaranteed transfer speed of 2 MB/s
• Class 4 offering a guaranteed transfer speed of 4 MB/s
• Class 6 offering a guaranteed transfer speed of 6 MB/s

If your SD storage memory card is rated too slow then as soon as the buffer in the host device reaches its upper threshold things will start to come to a rather abrupt end. When buying a memory card look for the indicator for the speed class which is usually a slightly broken circle (a large letter C) with a number inside either 2,4, or 6.

Learn more about the speed class of SD cards and the effect of fragmentation at the SD Association.