A method for operating a liquid crystal display having a panel with a back light includes applying a first gate signal starting a real data period followed by a second gate signal starting a black data period sequentially to gate lines of the panel, applying actual picture data signals to data lines of the panel during the real data period and reset data signals to the data lines of the panel during the black data period to drive cells of the panel during a frame along a gate line and controlling a ratio of the real data period to the black data period for a subsequent frame.