[MrFixr55]

Hi Winky Dink,

I know that this is an old post, but focus is not really about video per se, it is about raster. it is about focusing the electron beam to have the finest point when it hits the phosphor, and this is generally a compromise. Back in the day, the stations would broadcast a test pattern (Google test pattern for images). While the test pattern showed consumers that the station was broadcasting a signal, even before scheduled programs, much could be told by test patterns, including focus, horizontal width, vertical height, and linearity, correct contrast and even video fidelity (video amp bandwidth).