Abstract: An image is updated on a bi-stable display (310) such as an electrophoretic display in successive frame periods by accessing data defining a set of voltage waveforms for the successive frame periods. At least a portion of the bi-stable display is driven during the successive frame periods according to the accessed data so that a longer frame period (FT, 1302, 1304, 1402, 1502, 1602, 1702, 1802) is used during at least a first portion of the voltage waveforms, and a shorter frame period (FT?) is used during at least a second portion of the voltage waveforms. For example, the longer frame period may be an elongated frame period, which is the longest period during which each of the voltage waveforms has a respective constant voltage value.