A video imaging apparatus (10) comprises first and second cathode-ray tubes (12), each having an ultor electrode (12u) and a focus electrode (12f). A power supply generates an ultor voltage, which may have a fluctuating voltage component produced by beam current variations, and which is coupled to first and second ultor electrodes (12u) of the first and second cathode-ray tubes (12). A high voltage amplifier (22) generates a dynamic focus voltage component at a frequency related to a deflection frequency. A combining network (34) combines the fluctuating voltage component and the dynamic focus voltage component to develop a combined, dynamic focus voltage. The combined, dynamic focus voltage is coupled to each of the first and second focus electrodes (12f) for developing from the combined, dynamic focus voltage each of a first dynamic focus voltage at the first focus electrode (12f) and a second dynamic focus voltage at the second focus electrode (12f).