Jotho said:
Having read about the new 40mm pancake and considering getting myself one, I wonder if the MKIII supports the STM function in that lens? I am vey new to video having only so far shot family and golf in automatic settings only. If anyone could enlighten me I would be very thankful. Also, does this mean that it will refocus on new objects? Thanks in advance!
STM refers to the type of motor in the lens, it works with any camera. Its a stepper motor that focuses reasonably quickly and silently.
Autofocus while taking video is a function of the camera body, and the 5D MK III will not autofocus while taking video.
The T4i will autofocus during video, but only slowly. Its not fast like a camcorder. The thing that makes autofocus work during video for the T4i is the phase detect sites located in the sensor. They not only give a rough focus calculation, but tell the contrast detect AF which direction to move the lens, so it does not rack out to try to find focus when it should rack in. The T4i is the first to do this, but we will see some version of this in every new DSLR in the future.