The Vertical Resolution is limited by the number of horizontal scanning lines. In PAL it is 625 lines and in NTSC it is 525 lines. Using the Kell or aspect ratio factor the maximum vertical resolution is .7 of the number of horizontal scanning lines. Using this the maximum vertical resolution is PAL 625 X .75 = 470 lines NTSC 525 X .7 = 393 lines Vertical resolution is not critical as most camera manufacturers achieve this figure.