When shooting video with an HD DSLR, you have to hold the camera out in front of you and use the cameras LCD as the view finder. Which happens to be one of the least stable ways to hold the camera. You can’t bring the camera up to your face to stabilize it like you can when taking pictures. You have to use the view finder as the mirror locks up exposing the censor when shooting video much as it does for liveview photography. And that blacks out or obstructs the view finder.
Apart from that, you have to keep your subject in focus, even outdoors. And this is where the LCDVF comes in handy.
What does the VCDVF do?
LCD ViewFinder turns your HD DSLR LCD screen into a huge electronic viewfinder for precise image evaluation – it’s like viewing a 42″ screen from 140cm (4.6 feet).