2. Fast AF Live View Mode (shown in the top image):The smaller sub-mirror will move out of the way and the main mirrorwill rotate to a different angle to take advantage of its translucentproperties, which will allow light to pass through to the image sensor,while at the same time reflecting a portion of the light to thephase-difference AF sensor. This is what we all want - fast, accurateautofocus during Live View.