SDHC (short for Secure Digital High Capacity) Memory Cards are the most popular form of external storage for cameras, camcorders, mobile phones, and a host of other electronic devices. An SDHC memory card can store high-definition photos, video and audio, and can easily be transferred from one device to another.
The SDHC memory card expands on the original SD specification, allowing for greater storage capacity beyond the 4 GB limit for SD cards. Although almost all newer devices will support SDHC cards without problems, note that many older devices built to the original SD specification will not handle SDHC cards.
Check with the manufacturer of your device to see if there is a firmware update available that will allow your device to use an SDHC memory card. Note that any device that supports SDHC will also support the older SD cards as well.
The SDHC memory card is available in sizes from 4GB to 32GB. It is available in three different sizes: SDHC, miniSDHC, and microSDHC. The mini and micro formats were created for use in smaller electronic devices, such as mobile phones. All sizes share the same capacity and minimum speed capabilities. SDHC cards use the FAT32 file system, which is the same used in older versions of Windows.
An SD-sized adapter can be used for the miniSDHC and microSDHC cards so they can be used in devices that accept only full-sized SDHC cards. Often, the adapter will be packaged with the card itself.
There are four speed classes available for the SDHC memory card: Class 2 allows for a minimum transfer speed of 2MB/s. This allows for standard definition video recording. Class 4 has a minimum transfer speed of 4MB/s, while Class 6 has a minimum transfer speed of 6MB/s. These speeds are applicable for high definition video recording.
The fastest speed class, Class 10, has a minimum transfer speed of 10MB/s and allows for full simultaneous HD recording. Check the instruction manual that came with your device to determine which speed class is appropriate for your device.
Some devices have an SDIO slot, which can take both SD and SDHC cards, as well as small devices such as GPS navigators, Bluetooth devices, network adapters, modems and a slew of other possible devices.
The SD specification is based on an older memory card standard called the MultiMediaCard, or MMC. Some devices that use SD cards can also read MMC cards. SD cards were manufactured to compete with the proprietary Memory Stick standard created by Sony. The SD format was created by SanDisk, Matsushita, and Toshiba, and was first introduced in 1999.
The next generation of SD cards, SDXC, has recently been introduced. SDXC cards can handle up to 2TB of data, with transfer speeds up to 100MB/s! It uses Microsoft’s exFAT filesystem for portable drives. The first SDXC cards have just begun to show up on the market. Like SD and SDHC cards, it is likely that SDXC cards will not be compatible with devices that only support the SDHC standard.