I purchased a Rebel T3 for my daughter a few months ago. We are having trouble getting it to video. It keeps shutting off after a few seconds. It has a clean class 10 - 32gb card in it. Help please! (we have used a couple different cards in it, they all do fine & take excellent photos, just MAJOR problem trying to use the video mode) I have a T1i & have no trouble with the video on mine.
The manual may state Class 6 as the minimum speed for reliable HD video capture, but that it is most definitely not the fastest card supported by the camera.
The camera is able to take advantage of cards rated for speeds up to 45MB/s which should be at least 2x faster than the fastest Class 10 cards and about 4.5x faster than a Class 10 card operating at minimum spec of 10MB/s. A Class 10 card is rated for minimum throughput of 10MB/s write speeds. So, it should be between 7-8x faster than a Class 6 card performing at it's specified minimum 6MB/s speed.
So you really need to be looking at the write speed of the SD cards you buy. But, this assumes that the SD card is the problem which it may not be.