Memory cards allow us to capture life’s important moments with our still or video cameras, phones and even tablets, and share them with family and friends. These versatile cards also store different kinds of data, like music, spreadsheets and other files for use with laptops, smartphones and other devices..

But with so many different options, purchasing the right memory card can be a tricky process. 

To help with your decision, consider these three important factors when selecting a memory card: format, class and capacity.

Memory Card Format

Memory cards come in a variety of formats, including CompactFlash, SD, SDHC, SDXC, microSD, microSDHC and microSDXC. But what do all these terms mean? Which format is right for you?

CompactFlash vs. SD vs. microSD

CompactFlash, SD and microSD refer to different physical formats of memory cards. They are each different sizes, and your device determines which type of card you need. Consult your user’s manual, they often specify the card format required. Another option is to check the card slot on your device, usually a small logo will indicate the card format required.

Generally, CompactFlash is an older format, not so commonly found. SD cards are the standard for most point-and-shoot and DSLR cameras, while microSD cards are frequently used with action cameras, smartphones and tablets. The microSD cards can also be used with an adapter in SD slot applications, making them extra versatile.

Memory Card Capacity

HC vs. XC

The other letters in the different format descriptions (e.g. SDHC, microSDXC) refer to the capacity range of the card. The SD association defines memory card capacities as follows:

SD or micro SD:
What it means: This is the original designation used by the SD association.
Capacity of card: Up to 2 GB

SDHC or microSDHC:
What it means: HC stands for "High Capacity" 
Capacity of card: Between 4 and 32GB (Formatted with FAT32 system for file interchange)

SDXC or microSDXC:
What it means: XC stands for "Extended Capacity"
Capacity of card: Over 32GB (Formatted with exFAT file system for interchange)
 

The capacity of card you need is determined by the type of files you are working with. For basic snapshot photography, a lower capacity  SDHC or microSDHC card may be sufficient, however, when working with high megapixel photos, RAW format images or video, higher capacity cards will give you the storage capacity  to capture  more images or video footage.

IMPORTANT: SDXC and microSDXC cards may only be used with SDXC host devices. Consult your user manual to determine compatibility with your device.
Memory Card Class. Use caution when reformatting XC cards using a PC, as your computer system must support exFAT file system to properly format an XC card.

Memory Card Class

A memory card’s class is tied to the performance specifications of the card, specifically the minimum write speed for the card. The SD Association recognizes four different speed classes associated with the form HS (High Speed) bus interface:

• Class 2: 2MB/s minimum write speed
• Class 4: 4MB/s minimum write speed
• Class 6: 6MB/s minimum write speed
• Class 10: 10MB/s minimum write speed

As video recording technology further advanced, the need for performance specifications beyond Class 10 became apparent. As a result, the SD Association added additional performance designations for UHS (Ultra High Speed) interfaces and UHS Speed Class.

Bus Speed

Bus speed is the speed with which your device’s internal interface is capable of reading/writing data. To maximize performance, look for the bus speed markers on memory cards that match the bus speed of your device, e.g. If your camera is a UHS-I device, look for a memory card that is classified as UHS-I. This information should be found in your user’s manual.

UHS designates “Ultra High Speed” interface, which has a maximum theoretical bus speed of 104MB/sec (UHS-I) or 312MB/sec (UHS-II). For maximum performance you should select memory cards which are matched to the bus type (UHS-I or UHS-II) of your host device.