The Secure Digital memory card has been a major innovation in data storage, its small size and wide adoption allowing for more compact cameras and greater interoperability between devices like cameras, camcorders, and computers. Recently, however, the previously straightforward Secure Digital memory cards have been complicated by the introduction of Secure Digital High Capacity, or SDHC, cards. While SDHC cards have brought with them many positive aspects, they have also generated a lot of confusion among consumers who are having trouble sorting out the differences. This brief guide should help clear things up.
Standard SD cards are available in capacities up to 2GB, at present, while SDHC cards are now available in capacities between 4GB and 32GB. That's a tremendous amount of data for such a small card. The differences between SD and SDHC cards (apart from the obvious capacity difference) are largely technical, such as the different file systems each uses.
By providing small and affordable flash memory in high capacities, SDHC cards have made possible the introduction of digital camcorders that record high-definition video directly to an SDHC memory card. Additionally, this has provided digital cameras with the ability to record longer and more detailed video clips (including clips shot in high-definition).
Compatibility is a major sticking point for consumers. If you have an older camera, one purchased over two years ago, it probably is not compatible with SDHC cards at all. Newer cameras, however, can accept both older SD cards as well as the new SDHC formatted cards. Just be sure to check your owner's manual to be sure that your camera is capable of reading SDHC cards before you purchase one. Otherwise, you'll be stuck with a memory card you can't make use of.