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SD, SDHC, SDXC Memory Cards Explained

Removable flash memory cards are small, thumbnail sized electronic chips used to store video, still photos and sound. While camcorders have long included flash memory card slots for saving still photos, it’s only recently that they’ve started using flash memory cards to replace tape, DVD and hard drives as the main storage medium in a camcorder.

SD/SDHC Cards

Every camcorder manufacturer except Sony has used Secure Digital (SD) memory cards and its newer upgrade Secure Digital High Capacity (SDHC) for their flash memory card-based camcorders. Sony has used their Memory Stick cards, but in 2010, even Sony has now moved to SD and SDHC cards as well as their Memory Stick cards in their flash based camcorders.

SD/SDHC Card Capacities

SD cards are only available up to 2GB capacities, while SDHC cards are available in 4GB, 8GB, 16GB and 32GB capacities. The higher the capacity, the more video the card can store. If you’re purchasing a standard definition camcorder, you can get away with purchasing an SD card. If you’re considering a high definition camcorder that uses flash memory cards, you will need to purchase an SDHC card.

Compatibility

The majority of camcorders on the market accept both SD and SDHC memory cards. If your camcorder says it’s compatible with SDHC cards, it can also accept SD cards. However, if it only accepts SD cards, it cannot accept SDHC cards. Even if your camcorder accepts SDHC cards, it may not support all cards. Lower cost camcorders may not support higher capacity (16GB, 32GB) SDHC cards.

Speed

The speed of a memory card is critical, especially with a high definition camcorder. Slower SD/SDHC cards can be overwhelmed by the amount of data being fed to them by a digital camcorder. Put a slower card into your camcorder, and it may not even record at all.

What Speed Do I Need?

SD/SDHC cards are broken down into four classes:

Class 2, Class 4, Class 6 and Class 10.

Class 2 cards offer a minimum sustained data rate of 2 megabytes per second (MBps), Class 4 of 4MBps and Class 6 of 6MBps and Class 10 of 10MBps. The speed class should be displayed on the card.

For standard definition camcorders, an SD/SDHC card with a Class 2 speed is all you would need. It’s fast enough to handle the highest quality standard definition video you can record. For high definition camcorders, get a Class 6 card.

SDXC Cards

The SDXC card looks like your average SD/SDHC card, but will eventually boast capacities as high as 2TB and data speeds as high as 300 MBps.

SDXC vs. SDHC vs. SD Card

SDXC cards are essentially a higher capacity version of the SDHC card (which itself is a higher capacity version of the original SD card). SDXC cards start at capacities of 64GB and can grow to a maximum theoretical capacity of 2TB. By contrast, SDHC cards can only store up to 32GB of data and the SD card can only handle up to 2GB.

SDXC Card Speed

In addition to offering higher capacities, SDXC cards are also capable of faster data transfer speeds, with a maximum speed of 300MBps. In contrast, SDHC cards can achieve up to 10MBps. To help you find the right speed, SD/SDHC/SDXC cards are broken down into four classes: Class 2, Class 4, Class 6 and Class 10. Class 2 cards offer a minimum sustained data rate of 2 megabytes per second (MBps), Class 4 of 4MBps and Class 6 of 6MBps and Class 10 of 10MBps.

SDXC Card Cost

SDXC cards began to filter onto the market in late 2010 and early 2011. As with any new memory format offering high capacities and faster speeds, it's going to cost you more than lower capacity, slower SDHC cards. However, as more flash memory card makers offer SDXC cards, the costs should drop rather sharply over the next two years.

SDXC Card Compatibility

Most cameras and camcorders introduced in 2011 support SDXC. Support is more limited in cameras and camcorders introduced in 2010. If a camera takes an SDXC card it will always work with SDHC and SD cards. Always check your owner's manual for compatibility.

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