Using a newly-developed high-speed digital optical system, we measured the luminosity profiles of four leader/return stroke sequences within a flash occurred on a high tower. By analyzing those profiles, we obtained two simple expressions to characterize the light pulse decay features of subsequent return strokes along the channel bottom 210 m. These expressions can be extended to return stroke pulse currents and be easily included in return stroke modeling. In addition, we found that the peak light intensity of a leader and its following return stroke at various heights correlates positively in the channel bottom 210 m.