I think you got the spec wrong, what I read from Red Dot forum "The 4K video is captured at 1:1 on the sensor, meaning that each pixel on the sensor yields one pixel on the final video. So, to this end, the 4K capture area is a cropped section on the larger sensor. While I was pretty excited about the prospect of 4K on such a large sensor, from a quality perspective, this approach is a better one. In 1080p FullHD mode the entire area of the sensor, cropped to 16:9, is used. I imagine video guys everywhere drooling over the prospect of shooting on such a large sensor through the incredible range of S glass.". So there is no waste of pixel, at least not in fullHD.