I have a Transcend 8GB class six card for my T2i. It writes video fast enough without a problem. I bought a Sony 16GB class ten for the faster speed and a little extra storage space. It will not write fast enough to record video. I thought Sony would be a quality product but now realize it is not. I bought it off of Ebay so is it possible I got a knock-off? What brand and where am I safe buying a new sd card?