Canon 650D Tear Down by chipworks, they have written about Phase detection and auto-foucs system,
Canon 650D Tear Down by Chipworks
In short, this auto-focus capability works at the pixel-level to enable the camera to better shoot video. It represents a significant improvement over what is available in your basic handheld device. We’ll discuss more on the sensor technology later, but it means that the purchase decision for the entry level DSLR consumer isn’t determined by megapixels alone. Nor does it require an explanation on the benefits of larger versus smaller pixels, light pipes, or other means of improving light capture. It focuses (pun intended) on easy focusing to let the buyer focus (pun intended) on what matters (and can be upgraded) – lenses and accessories..
Below is a list of other parts identified in the Canon T4i Rebel:
See the full report at chipworks
See more Inside 650D / T4i | See more about Canon 650D
