SDHC cards explained (Secure Digital High Capacity cards)
- Fri, 4 Dec 2009
Let's assume that you own an 8MP compact camera that supports SD media, and that you take around 250 images between each unloading of your memory card. You should only ever need a memory card with a capacity of around 2GB.
The recent arrival of Secure Digital High Capacity (SDHC) cards has allowed this capacity to be extended, with Panasonic and Sandisk having both recently unveiled 32GB SDHC cards. To fit this amount of information into such a small space is impressive, but whether we need such capacities is a different issue. So, is there a method to their apparent madness?
Panasonic and Sandisk are, in fact, two of the companies who originally developed SD media, along with Toshiba, so their advances should come as no surprise. Standard SD cards aren't capable of storing such large amounts of data because of the way they are formatted, by the File Allocation Table (FAT). Whereas standard SD cards used the FAT12 and FAT16 systems, the FAT32 system was utilised to handle the different method of data allocation for higher-capacity cards. Because of this, not all cameras are compatible with SDHC cards (though almost all newer models are and SDHC cameras still accept standard SD cards), so you should check before buying one that it will be compatible with your camera.
Since its inception, the range of companies that have adopted the SD format for their products has spread rapidly. In one format or another, SD media is supported in a plethora of electronic devices, from PDAs and mobile phones to satellite navigation systems and gaming consoles.
While it may seem excessive to use such capacities for standard digital compacts, the format is also supported in mid-range and professional DSLR models, such as Pentax's 14.6MP K20D and Canon's 1D series. But it's in video cameras where SDHC media arguably finds its most useful purpose, with the sustained write speeds and high capacities making it perfect for recording hours of High Definition video. In fact, Panasonic claims that its 32GB SDHC card can store an impressive 12 hours of HD footage.