We saw from the example of Benedict XVI that a pope after abdication does not revert to the title of Cardinal, with the qualification of Eminence. Rather, he retains the papal title with the qualification of Holiness: it's just that he would add the qualifier of EMERITUS.

However, it has been said that he loses the designation of HOLY FATHER: is this correct? And does this happen at the moment of abdication -- even when the Catholic Church is in a state of SEDE VACANTE (meaning that no successor has yet been elected)?