Most of the digital camera and camcorder are able to record HD video nowadays. And most of them are using SD card which have SDHC and SDXC standards. The writing speed is very important as you don’t want to miss recording any frame of the video. The speed class rating is based on minimum writing speed of the SD cards. There are class 2, class 4, class 6 and class 10 SD cards in the market now.