Decoding Memory Cards


What do the numbers and letters on my memory card represent?
Ritu Saha, New Delhi, via email

Let’s start with the most obvious. The numbers preceding GB refer to the storage capacity of the card. On the other hand, SD/SDHC/SDXC are a kind of rating system for the capacity of the card. SDHC cards offer between 4GB and 32GB of space, while SDXC cards go much higher.

The term 95MB/s as shown on the card above, refers to the read speed of the card. This tells you the speed at which data can be read and transferred from the card. Some cards may also include the write speed, which tells you how fast data is written on to the card. It is also represented by the number in a circle which represents the Speed Class. Class 10 means that the card can record regular Full HD video while a Class 6 card is good for HD video and lower.

The number inside the symbol ‘U’ denotes the UHS Speed Class—a higher classification is needed when you require faster writing speeds for high bit rate video. UHS I, for example, refers to a minimum write speed of 10MBps. UHS Speed Class 3, on the other hand represents a minimum writing speed of 30MBps and is required for 4k video recording.

This article originally appeared in the February 2015 issue of Better Photography.

Tags: Memory Cards, ask the expert, SDHC