Well for a start, Nick, there isn't a single electron beam in a colour TV, there's three. There's an electron gun for each colour. And if you've ever done a "purity" adjustment on a CRT, you would know that the purpose of this is to make the beam from the red gun strike the red phosphors, not overlapping ones ! If you get this adjustment wrong, you can end up with some very dark pictures, because the beam is hitting the shadow mask, and not the phosphor dots.welwynnick said:....... The electron beam can never register exactly with any one particular phosphor "pixel" or line, and it doesn't try to. It is always set up so that the beam spot is bigger than the phosphors, and it always overlaps a few of them.