I have always used SD Cards (Secure Digital) for my cameras, so when I purchased the Panasonic HM-TA1 Video Camera, I was surprised to learn I needed an SDHC card (Secure Digital High Capacity) card. What is the difference? SDHC cost a lot more, but they must be doing something special. Here's the gist:
SDHC - Secure Digital High Capacity memory cards are flash memory cards with a minimum capacity of 4GB (gigabytes). SDHC cards are the same size as an ordinary SD Card - about the size of a postage stamp.
Secure Digital Cards have been around for almost a decade and SDHC Cards are a newer version developed for use with digital cameras and other devices that don't just require a higher capacity card, but also one that comes with higher performance. Here is something I found on Wikipedia: "SDHC cards are designed for devices that are compatible with the SD 2.00 specification. Products designed exclusively to support previous SD specifications 1.0 and 1.1 will not be able to utilize SDHC cards".
This is confusing (kind of), but you can use an SDHC card as a SD card, but not the other way around.
There is also a new feature out - "Classification of Data Transfer Speed (DTS)".
SD cards can record video up to 40X (6MB/Sec), but it starts slow (like, 0.1 MB/Sec) and then increases to 6MB/Sec (40X speed). It is an average speed recording. However, an SDHC card starts and finished at 6MB/Sec - 40x Speed, but has a top speed of 20MB/Sec - 133x Speed. That means your video is very clear and crisp on that high resolution flat screen!
Of course, the SDHC cards are more expensive than SD cards, but you get a far better quality.
I found that I had anything from a 512 MB SD card to an 8 MB SD card. There just was no point in having all these loose cards. Now with an SDHC, I can record more video at a higher quality and capacity. So it's worth the money in the end. You can get NEW cards at a cheaper price on Amazon, but I would advise against getting a used card. Like the adage goes, "You just don't know where that thing has been!"