Abstract: Disclosed are apparatus and method for applying a uniform electrostatic charge to an electrophotographic film through use of a corona discharge electrode positioned close to the film, a high voltage AC potential source connected to the electrode and having a potential greater than the corona threshold potential of the electrode, and a high voltage DC potential source connected to the electrode in series with the AC potential source for biasing the AC potential source, the DC potential source voltage being less than the difference between the voltages of the AC potential source and the corona threshold potential of the electrode. The film is subject to a series of first corona discharges of the desired polarity, of which each discharge is alternated with one of a series of second corona discharges having the opposite polarity and of lesser intensity than the first corona discharges.