A look at Memory Cards

Today, we bring you a brief clarification of the SD card family and what to look out for when purchasing one for your device, be it a camera, camcorder, recorder or a mobile phone. Your device manufacturer will indicate the specific type of memory card you should use for your device. You can find this information on your device manual or spec sheet. Usually, they are centered around these three areas:

  • Memory Card Family
  • Speed Class and UHS Speed Class Rating
  • Physical Size of the SD Card

By the way, the ‘SD’ in SD Card stands for ‘Secure Digital.’

Memory Card Family

Currently, there are three main types of memory cards: SD, SD High Capacity (SDHC) and SD Extended Capacity (SDXC). The differentiating factor — you guessed right —  is storage capacity. Some devices will not recognize a card if the capacity is above its specification.

The capacity of SD Cards usually range between 128MB and 2GB and come with a default file system of FAT16. We will cover the different file systems in a separate post.

SDHC capacities range from 4GB to 32GB with a default file system of FAT32. SDHC works differently from standard SD cards, hence, this new format is not compatible with devices that only take SD cards. Most devices built after 2008 should be SDHC compatible.

SDXC cards have their storage capacities ranging from 64GB to a theoretical 2TB with a default file system of exFAT. This new format is, as expected, not compatible with host devices that only take SD or SDHC. Most host devices built after 2010 should be SDXC compatible.

Speed Class and UHS Speed Class Rating

Speed Class simply refers to the minimum guaranteed transfer (read and write) speed of memory cards. On the card, the speed class rating is written inside of a shape that looks like the letter “C.” Can you identify the speed class ratings of the cards above? Currently, there are classes 2, 4, 6, 8 and 10. Class 2 cards are designed for a minimum sustained transfer rate of 2MB/s; Class 6, 6MB/s and so on.

UHS (Ultra High Speed) gives a much faster read and write speed. We currently have UHS Class 1 which has a minimum transfer rate of 10MB/s with UHS Class 3 coming in at a minimum of 30MB/s! On the card, the UHS speed class rating is written inside of a shape that looks like the letter “U.” If you use a UHS memory card in a non-UHS host device, transfers will be at the Speed Class rating of the host.

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