What John said.

Next time I won't post anything BEFORE I get some morning coffee in me. I MEANT to say that the Y channel is derived MORE from the green channel and that this was specific to YUV colour space (as compared to RGB colour space) and was indifferent to whether the colour separation was via prism block (ie. 3 CCD/ CMOS) or via filter (ie. 1 CCD/CMOS).

My brain hurts now.