Fig. 4. Effects of angular target speed on response amplitude and image blur. (A,B) Mean response amplitudes V of 7 male (A) and 7 female (B) photoreceptors to simulated target stimuli, plotted against angular target speed . The male response is larger than the female response and demonstrates an optimum angular speed that increases with target size. (C,D) Mean angular response width _v of the same male (C) and female (D) photoreceptors to simulated target stimuli, plotted against angular target speed . At low speeds, response widths are less than the widths of the targets (indicated by dotted lines), especially in the male. At high speeds, response width increases with speed (motion blur).