 With odd field dominance the edit or switch occurs at the start of the odd field.With even field dominance the edit or switch occurs at the start of the even field (some equipment, such as vision mixers or switchers allow the field dominance to be set to 'none' which means the switch will occur on the next field boundary after the switch has been pressed).Interlacing divides the frame into two fields, each containing half the number of lines.